Flattened Form Research Articles

Platyamoeba stenopodia n. g., n. sp., a freshwater amoeba.

SYNOPSIS. Platyamoeba stenopodia n. g., n. sp., isolated from a lake in Alabama, is an amoeba with flattened form, usually more than 2.5 × as long as broad, the anterior half hyaline and the posterior half granular, with a single vesiculate nucleus at the posterior edge of the hyaline region. It forms a transitory floating stage with slender, hyaline pseudopods. Its cyst is spherical, uninucleate, with a smooth inner wall and a thinner, closely applied outer wall, which is often slightly wrinkled. Length of locomotive amoeba 15–36 μ diameter of cyst 7–11.5 μ Reproduction by binary fission with mesomitotic nuclear division, the nuclear membrane disappearing in prophase. The genus Platyamoeba is erected for amoebae including this organism; the type species is P. placida.

The morphological basis of embryonic movements in the light brown apple moth, Epiphyas postvittana (Walk) (Lepidoptera : Tortricidae)

A description is given of the morphological basis of the embryonic movements revealed in E. postvittana by time-lapse cinematography. The blastoderm gives rise to a broad germ band and serosal rudiment. The serosa spreads over the germ band, followed by the amnion. The germ band becomes cup-shaped, elongates, and turns on its side in the flattened egg before gastrulation begins. Only a small amount of the yolk of the egg is enclosed in the germ band. The remainder fills the amnioserosal space. As elongation continues, mainly through growth in the length of the abdomen, and segmentation takes place, the germ band becomes spirally coiled and convoluted within the flattened egg space. At the completion of elongation, the nervous system is well developed, segmental myoblasts are present, and the tubular stomodaeum and proctodaeum are linked by paired midgut strands. Shortening and dorsal closure eliminate the spiralling and convolution of the germ band and result in a tubular embryo with a large ganglionated nerve cord and large stomodaeum and proctodaeum, but with musculature still at the myoblast stage and midgut strands unchanged. Paired sheets of cardioblasts extending from the body wall to the midgut strands divide the ventral haemocoele from the dorsal haemocoele in the middle region of the body. A mesodermal sac covers the inner end of the stomodaeum and opens in the dorsal haemocoele. The tubular embryo now elongates, doubling its volume, reverses its position in the egg, and tucks the tail in beside the head. During elongation, the segmental myoblasts differentiate as muscle fibres. Towards the end of elongation and reversal, the midgut strands give rise to the midgut tube and the cardioblast sheets to the middorsal heart. When elongation and reversal are complete, the stomodaeal mesodermal sac is transformed into proventricular mesoderm. After further differentiation of striated muscle and secretion of the cuticle, the embryo ingests the yolk in the surrounding amnioserosal space and digests it before hatching takes place. Comparison of morphological structure with the movements displayed in the time-lapse record show that all elongation, rotation, spiralling, and convolution of the embryo before the onset of shortening is due to growth by cell proliferation and to accommodation of this growth within a fixed egg space of specific shape. In contrast, controlled muscular activity plays a major role in shortening and dorsal closure, in elongation and reversal of position, and in ingestion of excluded yolk. During shortening and dorsal closure, slow, generalized, possibly myogenic contractions are produced by the somatic myoblasts and appear to be responsible for the shape changes observed. During elongation and reversal, contractions are confined to the stomodaeal myoblast layer and result in rhythmic filling and emptying of the terminal stomodaeal sac. By this activity, fluid is transferred from the excluded yolk to the embryo and pumped along the dorsal haemocoelic channel, bringing about controlled elongation and reversal. In view of the coordination exhibited, and of the precocious development of the nervous system, it seems likely that this activity is neurogenic, even though the contractile units are still myoblasts. The final movement of reversal, tucking in of the tail, is due to somatic musculature, now differentiated as muscle fibres and showing twitches of probably neurogenic causation. Ingestion of excluded yolk is a precocious feeding activity, brought about by coordinated action of the larval feeding apparatus, and occurs only when the appropriate musculature has become differentiated as striated muscle. Although the morphogenetic movements of E. postvittana show modifications associated with the flattened form of the egg, they and their structural basis are, on comparative evidence, common to all lepidopteran embryos.

Fine structure of the respiratory lamellae of teleostean gills.

The blood-water pathway in respiratory lamellae of teleostean gills consists of an epithelial layer one or two cells thick, a basal lamina and a thin layer of cytoplasm which lines the blood lacunae. This layer of cytoplasm is formed by flange-like extensions of the pillar cells. The resulting location of the pillar cell perikarya between the surfaces of the blood lacunae is probably of paramount importance for maintenance of the flattened form of the lamellae.

Etude biometrique et statistique de Nummulites laevigatus Bruguiere dans les bassins de Paris et du Hampshire; implications stratigraphiques

Abstract Biometric and statistical analysis of approximately 4500 specimens of Nummulites laevigatus from the Paris basin and from Hampshire (Wight, England), indicates that this species belongs to the lower Lutetian (Eocene), and that the enclosing beds are equivalent to the Bracklesham and the Fisher beds VI and VII of England and the Bruxellian of Belgium. N. laevigatus forms only one biozone. Among the results of the study are the recognition of a diminishing frequency in the irregularity and loose coiling of the spire in favor of regularity and tight coiling, from the base to the top of the lower Lutetian, and the dominance of flattened forms in the older lower Lutetian outcrops.

Helical dislocations in crystals of lead iodide

Abstract The appearance of 'zig-zag' dislocation lines during the decomposition of crystals of lead iodide in the electron microscope can be explained by the climb of existing dislocations into a flattened helical form. The simple zig-zags are often distorted into cusped and looped forms and it is shown how these distortions may be accounted for by the elastic interaction between neighbouring segments of the helices. Such internal re-arrangement within helices is possible only as a result of the marked anisotropy of climb and glide processes in these particular crystals. The climb of arrays of dislocations leads to interactions between neighbouring helices. Some examples of such interaction are described and it is shown how these may lead to the formation of isolated loops of dislocation and double helices. An examination of the nature of loops formed in this way suggests an interesting possibility for the creation of new regenerative sources of glissile dislocations.

Factors Controlling the Change of Shape of Certain Nemertean and Turbellarian Worms

ABSTRACT Nemerteans and turbellarians have an inextensible fibre system around them in the form of a lattice of left-and right-handed spirals. The effect of this system on the change of shape on these worms has been analysed theoretically and compared with the observed behaviour of nine species of turbellarian and nemertean from widely differing habitats. The following theoretical relationships have been studied: (a) Variation of the angle between the geodesics and the longitudinal axis of the worm during changes in length, and the role of the fibre system in limiting changes in length of the animal. (b) The change in cross-sectional shape during changes in length. (c) The extension of the fibres and the extensibility of the worms, assuming the fibres of the lattice to be elastic. The species investigated conform with the theoretical predictions to varying degrees and have been grouped accordingly : (a) Geonemertes dendyi and Rhynchodemus biUneatus have low extensibilities and fit the prediction well. They are nearly circular in cross-section at all lengths as a result of their low extensibility and this is related to their terrestrial habit and need for water conservation. (b) Amphiporus lactifloreus, Lineus gesserensis and L. longissimus are moderately flattened in the relaxed position and have extensibilities between 6 and 10. They are marine crawling forms using cilia for locomotion and so must present a fairly large ciliated surface to the substratum. The fibre system does not limit contraction; the compression of the epithelial cells causes the observed extensibilities to fall a little short of the theoretical values. (c) Cerebratulus lacteus, Malacobdella grossa, Polycelis nigra and Dendrocoelum lacteum are very flattened forms and have very high theoretical extensibilities, but very low observed ones. The factors causing this are the thickness of the body-wall musculature (Cerebratulus), the limiting effect of longitudinal and circular reticulin fibres in the muscle layers, and the presence of dorso-ventral and diagonal muscles. Their flattened form is correlated with ecological factors (with swimming in Cerebratulus, with its parasitic life in the mantle of bivalves in Melacobdella) or with physical ones in turbellarians where a permanently flattened form is necessary for these worms to move by ciliary action.

Cytological and chemical studies of the growth of protoplasts of Bacillus megaterium.

Aeration of protoplasts of Bacillus megaterium in a succinate buffered nutrient broth led to marked growth similar to that already described by McQuillen, and the degree of chromatin synthesis in these growing forms prompted a combined cytological and chemical study. Growth was followed by phase contrast and by Feulgen stains, as well as by lipide phosphorus, nucleic acid, and protein analyses. In slide cultures, growth and compression led to monstrous flattened forms with readily visible, but coalescent nuclear structures. In fluid cultures, the protoplasts grew as phase dense spheres. Orderly reproduction of apparently discrete nuclear bodies was observed during the initial hours of spherical growth, but in older cultures, the chromatin arrangement tended to be more haphazard and was influenced by the concentration of Mg ions. In the same medium, protoplasts free of lysis showed a linear rise in optical density, while vegetative cells exhibited an exponential increase. However, protoplasts were able to synthesize DNA at the same rate as vegetative cells, but their increase of RNA was always less. Thus, as they grew, the ratio RNA/DNA fell. The lipide P increased in proportion to the expanding surface. With growth and lysis, large amounts of water-insoluble slime accumulated. Analyses indicate it to be a phospholipoprotein material containing some RNA.

The Improvement of Luster of Cotton

The results of swelling treatments which go beyond mercerizing at ordinary temperature indicate that there is an upper limit to the swelling of cotton, with increased luster as the objec tive. If this is exceeded, as it is with strong sulfuric acid or zinc chloride, and probably is with mercerization with caustic below 0°C, the luster is decreased, because the surface of the indi vidual fiber is roughened. Drastic shrinkage of yarn volume, combined with film formation and disappearance of fuzz, can leave the fabric very sheer and transparent, attributes often correlated with luster. Me chanical action on the plastic cellulose, or on films of cellulose or hydroxyethyl cellulose de posited from solution, can give increased luster through flattening and mechanical stabilization in the flattened form. These cellulose-affecting treatments tend to leave the fabric stiff, if they go beyond normal mercerizing. Other additive finishes act on luster either through film formation or by stabilizing mechani cal effects and controlling fabric structure. The more flexible thermoplastic resins can, with mechanical smoothing, produce an increase in the physical measurement of luster. However, this effect is less than that of mechanically smoothing the fabric without the thermoplastic resins, so the chief advantages lie in the other effects of these finishes, such as possible greater stability of the mechanical finish with the resin present. In the higher ranges of luster, the eye can discriminate between luster arising from film formation or flattening, and the type of luster arising from yarn and fabric structure and from mercerizing.

Phase Contrast and Electron Microscope Studies of the Appearance and Behaviour of the White Cells of Normal Human Blood

ABSTRACT The phase-contrast microscope has been used to study form and movement of human leucocytes and blood platelets in three types of preparation ; (a) warm sealed blood drops, (b) warm sealed films of leucocytes adhering to coverslips after incubation of blood drops at 37° C. for 30 minutes or more, and (c) warm sealed films of blood platelets obtained by similarly incubating drops of saline suspensions of these cells. Similar preparations to (b) and (c) were obtained on formvar films and studied in the electron microscope. Phagocytosis was studied in all the above preparations after adding suspensions of collodion particles or of Staphylococcus albus. The neutrophils were the most versatile cells seen in the above preparations. The amoeboid forms were the most mobile and phagocytic. Another form showed rapidly waving processes which gradually spread into a flat membrane on the glass. Flattened immobile neutrophils were still capable of phagocytosis. Bacteria which adhered to the cell surface moved over it towards the thicker central region of the cell where ingestion occurred. Eosinophils showed a mobile amoeboid form and flattened forms which were often very bizarre in shape. They did not phagocytose readily. Monocytes showed slowly moving amoeboid forms or forms with ruffle-like membranes around the cell. They were phagocytic. Lymphocytes were capable of amoeboid movement but did not flatten on glass and were not phagocytic.

THE COCKROACHES OF THE PROVINCE OF QUEBEC

For a long time, the order Orthoptera was a loosely interpreted group which has now been restricted to more homogeneous forms. The well known cockroaches which formed the family Blattidae are now considered as a séparate order under the name of Blattaria.The cockroaches are so well known that there is no need for a detailed description of their morphology. They are easily separated from the other insects by their soft bodies, by their oval and flattened form; the antennae are often longer than the body and are composed of many short segments; the head when at rest, is bent under and almost concealed by the pronotum, so that the mouth projects back to the base of the front legs.

HISTOLOGY OF THE DEVELOPING PITUITARY IN THE FROG AND THE TOAD: 10. On the Histology of the Developing Pituitary in the Frog (Rana t. temporaria) and in the Toad (Bufo bufo).

Summary1. The histogenesis of the pituitary of Frog and Toad tadpoles has been followed from the time of emergence from the egg‐jelly until they leave the water, and that of the young Frog to four months. The development of the thyroids, particularly in relation to the pituitary and to metamorphosis, and also that of the gonads has been followed.2. Histological differentiation of the two glands in both species commences at the same time and at the stage when the larvae become completely free‐swimming. Eosinophile granules appear in cells towards the posterior end of the anterior lobe of the pituitary, and minute droplets of colloid appear in the centre of groups of thyroid cells.3. There is a steady increase in eosinophiles and in the amount of colloid in the early stages up to the beginning of rapid hind‐leg growth. Colloid is not only stored but discharged during this period, when only eosionophiles are present in the pituitary. The early organization of the gonad proceeds meanwhile, seemingly independently of the pituitary.4. In the next period, which can be regarded as the most active period of metamorphosis since the hind legs grow rapidly, the fore legs appear and the tail is absorbed, the thyroid is extremely active, both in the formation and release of colloid. This activity is much more pronounced in the Frog than in the Toad, which develops later. A marked increase in the amount of thyroid tissue also occurs. The eosinophiles continue to increase in number but lose their staining power somewhat, possibly indicating an active discharge of secretion. These observations indicate that general body‐growth and thyrotropic function are associated with the eosinophile cells. A few faintly staining basophiles appear at this time in the anterior pituitary lobe in the Frog, and later in the Toad. They increase regularly but slowly and show no close relationship with thyroid activity. Basophiles can be seen also in the intermediate lobe, but remain few and primitive throughout early development.5. As the absorption of the tail is completed and the animals leave the water the eosinophiles continue to increase slowly and the basophiles to increase more rapidly, whilst the pars tuberalis becomes separated from the anterior lobe. The largely emptied vesicles of the thyroid become refilled with colloid and greatly distended, while the epithelial cells begin to lose their active cubical form and to take on the flattened form of the adult. The gonad is now becoming organized into a definite ovary or testis.6. The further development of the pituitary in the Frog up to the first hibernation period produces a gland in which the intermediate lobe still remains rather undeveloped but in which the anterior lobe is beginning to resemble that of the adult. Eosinophiles are deeply staining and adult in appearance, basophiles are much more numerous and are approaching the adult state both in proportion to eosinophiles and depth of staining, whilst neutrophils can be distinguished. The increase in number and maturity of the basophiles as the definitive gonads form supports the view that they are primarily sex‐stimulating in function.

Cicatrization of Foliage Leaves II. Wound Responses of Certain Broad-Leaved Evergreens

1. Leaves, as necessarily exposed organs, do not employ massive coverings, and so are constantly subjected to injury. 2. Following lesion, tissue collapse along wounded leaf margins usually leads to the prompt establishment of a protective barrier, the pseudocicatrice. 3. The cicatrice proper of wound cork forms slowly underneath, from living tissues protected by the pseudocicatrice. 4. The broad-leaved evergreens in comparison with mesophytic foliage have thicker leaves, heavier cell walls, and better developed cuticular layers. The wound responses are similar, but the process is slower in the thicker leaves and their protective structures involve much greater amounts of tissue. 5. The mature leaves of Berberis nervosa are unique because they are so rigid that the exposed tissues cannot collapse; consequently these leaves are unable to form a pseudocicatrice, and this in turn inhibits the development of any cicatrice. Such leaves are left open to fungal invasion and usually have masses of spores and mycelia in and along the wounded margins. 6. If younger leaves of the same plants are wounded, the dead tissues collapse into an efficient pseudocicatrice, while behind this is formed a massive cicatrice of wound cork, and such protected margins have no fungi. These leaves reveal a diminishing capacity for the formation of such protective barriers as they approach maturity, and show increasing amounts of fungi along their wounded margins. 7. The cicatrice proper is generally not initiated until several days after injury, and its complete development in broad-leaved ever-greens requires 20-40 days. While highly efficient, it is usually more elaborate than necessary, and corresponds in many respects with the healing tissues of tubers or other massive plant parts. 8. The pseudocicatrice is distinctively a foliar response. The structure and arrangement of cells in the leaf in combination with its thin and flattened form permit the ready collapse of tissues exposed by wounds, with favorable use of the cuticular layers. The pseudocicatrice, in addition to its protective value, sustains a causal relation to the development of wound cork and remains a permanent barrier along the wounded leaf margin.

Societies and Academies

LONDON. Geological Society, March n.—O. T. Jones: The geology of the Llandovery district (Carmarthenshire). The district lies east of the town of Llandovery, and extends for about 10 miles from north-east to southwest. It is divisible into a northern area and a southern area, each area the succession is fairly complete, but in between them it is greatly attenuated. In proceeding from south to north, certain lithological changes have been noted in the Lower Llandovery. The fauna in the rocks appears in the main to have been drifted into the area from an adjoining tract, lying probably nearer to the shore-line. In addition to the differential subsidence and uplift along lines trending north-east and south-west, there is evidence of repeated elevation and depression along nearly east-and-west axes. The axes of these transverse movements appear to have persisted during the whole of the Llandovery epoch, but there is no evidence of them in the Wenlock rocks.--G. Andrew: (i) The Llandovery and associated rocks of Garth (Brecon-shire). The Llandovery rocks lie north-west of Garth railway station, and extend from there in the direction of Newbridge. The Lower Llandovery rocks overlie the Bala with a sharp boundary, but with apparent conformity. The Middle Llandovery occurs in one small outcrop in the centre of the area, and is rapidly overstepped by the Upper"Llandovery in both directions. The Upper Llandovery consists of two types, a lower comprising sandy mudstones with Pentamerus oblongus, etc., and an upper of pale mudstones ("Tarannon Pale Shales "). (2) The relations between the Llandovery rocks of Llandovery and those of Garth. At Garth, as at Llandovery, the Lower and Middle Llandovery rocks are overstepped both north and south by Upper Llandovery or Wenlock deposits. At Garth they crop out Jin an elongated oval area; at Llandovery they form two roughly oval areas. The Middle Llandovery and the higher divisions of the Lower Llandovery are represented only in the central regions. These distributions are due to the fact that differential movements along nearly east-and-west axes (that is, transversely to the present strike) were in progress during the Llandovery epoch. The regions where the older Llandovery rocks are most complete were regions of persistent subsidence. The axes of elevation in both areas cross the present strike at practically regular intervals of about 5 miles, and the areas of subsidence are situated nearly midway between them. Linnean Society, March 19.—S. Hirst: Species of mites of the family Trombidiidae found on lizards. When more than one form occurs on the same host, a flattened form lives under the scales, and a rounded form between the toes or toe pads. In view of the considerable differences in the shape of the setae, etc., these are regarded at present as distinct species.-o Mrs. Muriel Roach: A study of the physiology of certain soil alga; in pure culture. Although a very few species carried on the synthesis of organic substance from carbon-dioxide and water through the agency of sunlight, the great majority of those studied grew much better when supplied with an additional source of carbon, glucose being especially favourable to many species. A single species was selected for a more detailed investigation of the effect of different organic substances on its growth in liquid media. The alga was able to grow in complete darkness, given a suitable supply of food, at about half the rate that it grew in the same medium in the light. The logarithmic values of the bulk for the first nine or ten days, in media completely favourable to the growth of the organism, lie on a straight line. The data indicate the importance of the compound interest law which evidently underlies the growth of the organism during the initial part of its growth. The theory of the auto-catalytic nature of growth does not appear to hold.-J. M. Brown: Some Collembola from Mesopotamia. Fifteen species of Collembola collected mainly in the neighbourhood of Bagdad and Amara, in Mesopotamia. Ten species and one variety are regarded as new. The Collembolan fauna of Mesopotamia shows much closer affinity with that of the Palasarctic than with that of either the Oriental or the Ethiopian regions.

XV.—The Formation of the Germ-Band in the Egg of the Holly Tortrix Moth, Eudemis nævana (Hb.)

During the spring of 1916, while making observations from an economic point of view on the Holly Tortrix Moth, Eudemis nœvana (Hb.), I found that, owing to the transparency of the egg and its flattened form, the development could be followed in the living egg in a general way with unusual clearness.Investigations have been carried out on the embryology of about eighteen species of Lepidoptera, but as far as I am aware no account has been published of the embryology of the Tortricidæ.

Mycenaean Vases at Torcello

In view of the importance of ascertaining the limits of the influence of the early civilization of the Aegean, the existence of four Mycenaean vases in the little museum at Torcello has a certain interest.This museum contains a miscellaneous collection of antiquities, some dug up in the island itself or coming from the ecclesiastical buildings close by, some from the adjacent islands in the lagoon. Amongst a number of vases of later date are the four in question.The first of these (No. 727) is a small pseudamphora of somewhat flattened form. The buff slip is decorated all over the body of the vase with bands of red glaze-paint. The spaces on the shoulder of the vase not occupied by the spout and handles are filled with parallel strokes gradually decreasing in length, which thus form the triangles of bars common on late Mycenaean ware.

Note on agate specimens from Monzie

Locality. These specimens were obtained from the Porphyrite formation, which for the most part divides the Lower Old Red Sandstone of the great centre valley of Scotland from the Clay Slate and Greywacké of the southern highlands. The exact locality of these agates is a small tributary of the Shaggie, on the left bank, and about three hundred yards north of the schoolhouse at Monzie. (See sketch map adjoining.) Proceeding up this stream from A towards B, as marked on the sketch, we find some interesting variations in the contents of the rock. Association. 1. At A a reef of Carytes runs for some yards on the left bank of the stream. I am inclined to think this reef persists probably as far as B, as I find there in the bed of the stream fragments of the mineral. 2. Further on just above the point where an old road (now disused) crosses the stream, we find amygdaloidal porphyrite. The rounded enclosures of this are mostly calcite, but here and there they are composed of red or blue chalcedony, and some of them are true agates. 3. Still further up the burn we reach the place where the specimens about to be described are found. 4. Then again, about the old road to Sma’ Glen, the rock is intersected by jasper veins. Common Characteristics. 1. Irregularity of shape—so markedly different from the rounded, oval, or flattened form of the common

II. Note on the intracellular development of blood-corpuscles in mammalia

If the subcutaneous connective tissue of the new-born rat is examined under the microscope in an indifferent fluid, it is found to consist chiefly of an almost homogeneous hyaline ground-substance, which is traversed by a few wavy fibres, and has a considerable number of exceedingly delicate, more or less flattened cells scattered throughout the tissue. The cells here spoken of are of course the connective-tissue corpuscles. They are not much branched as a rule (at any rate their branches do not extend far from the body of the corpuscle), and they are mainly distinguished by the extraordinary amount of vacuolation which they exhibit—by which is meant the formation within the protoplasm of minute clear spherules, less refractive than that substance, and probably, therefore, spaces in it containing a watery fluid. The nuclei, of which there is generally not more than one in each cell, are frequently obscured by the vacuoles, but, when visible, are seen to be round or oval in shape and beautifully clear and homogeneous; they commonly contain either one or two nucleoli. It is from these cells that the blood-vessels of the tissue are formed, and within them, red, and perhaps also, white blood-corpuscles become developed. Of the vacuolated cells above described some possess a distinct reddish tinge, either pretty evenly diffused over the whole corpuscle, or in one or more patches, not distinctly circumscribed, but fading off into the surrounding protoplasm. Others contain either one, two, or a greater number of reddish globules, consisting apparently of hæmoglobin. These vary in size, from minute specks to spherules as large as, or even larger than, the red corpuscles of the adult: in cells which are apparently least developed it is common to find them of various sizes in the same cell; whereas cells which are further advanced in development are not uncommonly crowded with hæmoglobin-globules, tolerably equal in point of size, and differing from the adult corpuscle only in shape. It is important to remark that there is, at no time, an indication of any structure within the globules resembling a nucleus: the nucleus of the cell also appears, up to this point at least, to undergo no change. In fact the formation of the hæmoglobin-globules reminds one rather of a deposit within the cell-substance such as occurs in developing fat-cells, the difference being that in the latter case the deposited globules eventually run together into one drop, whereas in the former they remain distinct as they increase in size and eventually take on the flattened form.

NOTES ON HADENA XYLINOIDES

On the 17th of June I captured a female specimen of Hadena xylinoides, early in the evening on a sugar cask. Having confined it in a pill box I laid it aside and did not examine it again until the 20th, when it was observed that a number of eggs had been deposited. These, although examined casually by the microscope, I neglected taking a minute description of. They were about medium size, of a flattened conical form, greenish in colour, and ornamented with many striæ. The eggs hatched on the 24th of June, when the following description of the young larva as seen under a common eye-glass was taken

Palichthyologic Notes. No. 2.—On the Affinities of the Genus Platysomus

Some of the earliest writers on Palæontology were acquainted with the Petrified Fishes not uncommonly found in the Kupferschiefer of Mansfeld and its vicinity, on which Agassiz established his genus Platysomus . Figures are given of these fishes under the name of Rhombus diluvianus major and minor , by Wolfart*, Scheuchzer†, Knorr and Walch‡ and others. More recently De Blainville and Germar have described them, assigning them, in consequence of their deep and flattened forms, to the genus Stromateus §. Agassiz satisfied himself that this determination, founded on outward characters, unaccompanied by structural coincidences, could not stand ∥; at the same time the unusual combination of this form of body with a heterocerqual tail and other anatomical peculiarities evidently raised doubts in his mind as to the true position and affinities of the genus ¶. Mr. King of Newcastle-on-Tyne has recently submitted to me a specimen of Platysomus macrurus from the magnesian limestone of Ferry Hill, which clears up the obscurity that has hitherto enveloped the subject, and provs from the characters of the dentition that this genus should be removed from the Lepidoidei to the Pycnodonti . The dentary portion of the lower jaw, as shown by this specimen, fig. 1, is a dense triangular bone, very similar to the Pycnodont jaws found at Stonesfield and elsewhere. Two rows of teeth are seen, the outer one composed of eight or nine small tritores, the inner one containing five considerably larger than the outer ones. The teeth are al clavate in form. The crown