Hypertonic Sea Water Research Articles

Intracellular calcium release and the mechanisms of parthenogenetic activation of the sea urchin egg

Parthenogenetic activation of Lytechinus pictus eggs can be monitored after injection with the Ca-sensitive photoprotein aequorin to estimate calcium release during activation. Parthenogenetic treatments, including the nonelectrolyte urea, hypertonic sea water, and ionophore A23187, all acted to release Ca 2+ from intracellular stores. Ionophore and urea solutions release Ca 2+ from the same intracellular store as normal fertilization. This intracellular store can be reloaded after 40 min and discharged again. Hypertonic medium appears to release Ca 2+ from a different intracellular store. Treatment with the weak base NH 4Cl did not release intracellular Ca 2+ but did result in a momentary Ca 2+ influx if Ca 2+ was present in the external solution. Ca 2+ influx was not required for ammonia activation.

Eel esophagus as an osmoregulatory organ.

Ion and water permeabilities were measured in the isolated esophagus of the eel (Anguilla anguilla and A. japonica), and compared with those in the stomach and the intestine. The freshwater eel esophagus was impermeable both to Na+ and Cl- ions and to water, whereas permeabilities to the ions increased selectively after seawater adaptation. The ion permeabilities of both the freshwater and the seawater eel stomach were lower than in the seawater eel esophagus, although water permeability was greater than in the esophagus. Sea water enclosed in the lumen was diluted three times more efficiently in the seawater eel esophagus than in the stomach. The intestinal permeabilities were greater than those of the esophagus and the stomach, and increased after seawater adaptation. In the eel, ingested sea water seems to be diluted mainly in the esophagus by passive diffusion of the ions into the blood without addition of water. After further but less important dilution in the stomach with salt removal and with water addition, the water is absorbed by the intestine, following active absorption of the ions. Thus the eel in sea water is able to replace water lost osmotically by drinking hypertonic sea water.

ACTION OF HYDROSTATIC PRESSURE ON SEA URCHIN CILIA

The effects of hydrostatic pressure on the cilia of sea urchin embryos (Arbacia and Strongylocentrotus) were investigated. At a pressure of 10,000 psi the swimming blastula and early gastrula embryos became less active. They lost their translational movement and began to rotate slowly on the bottom of the chamber; in about 10 min all movement stopped and essentially all cilia had fallen from the embryos. At lower pressures and with longer durations the embryos were differentially affected and there was considerable variation in the number of cilia removed from individual embryos. With pressures of 6000 psi for 60 min the majority of the embryos lost more than 50% of their cilia. Arbacia embryos were more pressure-sensitive than Strongylocentrotus embryos.Following deciliation with hypertonic seawater, hydrostatic pressure above 5000 psi was found to block regeneration for the duration of the pressure treatment. At 6000 psi and above the regeneration delay was in excess of the duration of pressure treatment; the regeneration delay was directly proportional to the duration of treatment. At pressures lower than 5000 psi sea urchin cilia were able to regenerate under pressure but at a reduced rate relative to controls. Pressure treatment does not affect regeneration rate following decompression.The results are discussed in terms of the known effects of pressure on cellular systems.

Electron microscope studies of frozen-substituted marine eggs. 3. Structure of the mitotic apparatus of the first meiotic division.

AbstractEggs of the clam Spisula solidissima were studied by freeze‐substitution techniques at the time of the first meiotic division. The mitotic apparatus is organized into regions containing microtubules, endoplasmic reticulum, ribosomes and mitochondria which surround densely stained amorphous regions. The amorphous regions, which appear to be channels running through the mitotic apparatus, are radially arranged in the asters and are parallel to the spindle axis. Microtubule‐associated particles, each about 250 Å in diameter, are arranged in crystalline arrays around the microtubules of the mitotic apparatus. After a period of time in hypertonic sea water the mitotic apparatus disappears and the microtubule‐associated particles remain aggregated in hexagonally packed crystals. Histochemical tests suggest that the particles are composed of polysaccharide material. Other particles and inclusions show orientation relative to the mitotic apparatus axis or show non‐uniform localization in the egg. The possible meaning of such localization and orientation in the physiology of the egg is discussed.

A cytological study of the centrifuged whole, half, and quarter eggs of the sea urchin, Arbacia punctulata.

While the ooplasmic components of centrifuged eggs of Arbacia punctulata do not stratify in homogeneous layers, we have obtained the following strata beginning with the centripetal end: lipid droplets, pronucleus, clear zone, mitochondria, yolk, and pigment. Whereas mitochondria may be found mingled with yolk bodies, we have never observed lipid droplets nor pigment bodies among any of the other inclusions. The so-called clear zone contains a heterogeneous population of inclusions: annulate lamellae, heavy bodies, Golgi complexes, and rod-containing vacuoles. The peripheral cortical granules of immature (germinal vesicle stage) and of mature eggs are not dislodged from the cortical ooplasm with the centrifugal force utilized. When the eggs are treated with urethane, prior to centrifugation, the cortical granules of mature eggs abandon their peripheral position. Further centrifugation of the initially stratified eggs produces nucleated and nonnucleated halves and the centrifugation of the halves results in quarters. The cytology of the halves and quarters is discussed. The halves and quarters have been activated with either sperm or hypertonic sea water. With the exception of the nucleated halves, we were unable to obtain plutei larvae from the other fractions (red halves and quarters). We believe that the lack of development of the various fragments is a function of the balance of particular inclusions necessary for differentiation.

A cytological study of artificial parthenogenesis in the sea urchin Arbacia punctulata.

Eggs of the sea urchin Arbacia punctulata were artificially activated with hypertonic seawater. The artificially activated eggs undergo the cortical reaction which is not distinguished by a wavelike progression as in the case of inseminated eggs. The cortical granules are released at random loci at the surface of the egg and result in spaces separated by large cytoplasmic projections. Unreacted cortical granules and ribosomes are found within the matrix comprising the large cytoplasmic projections. No "fertilization cone" is formed. The subsequent release of additional cortical granules results in the formation of a continuous perivitelline space, 15 min following activation. 85 min postactivation, an organization of annulate lamellae, endoplasmic reticulum of the smooth variety, and microtubules around a centriole is observed prior to nuclear division. Before the breakdown of the nuclear envelope a streak stage is formed. The streak is composed of a central core of annulate lamellae and is encompassed by endoplasmic reticulum and vesicular components. Condensation of chromatin is followed by the establishment of the mitotic apparatus. Centrioles were not found in the mature egg; however, they are present after activation prior to the first nuclear division, in the four-cell embryo, multicellular embryo, and at blastula. Artificially activated eggs have been observed to develop to the pluteus stage in more than 50% of the eggs treated.

Cilia regeneration in the sea urchin embryo: evidence for a pool of ciliary proteins.

Late gastrulae of paracentrotus lividus regenerated cilia after being deciliated in hypertonic sea water. Regeneration was not affected by actinomycin D or puromycin. Actinomycin D also did not affect ciliary protein synthesis during regeneration, although overall embryonic synthesis was depressed. Puromycin inhibited both total embryonic and ciliary protein synthesis. The data indicate that ciliary protein synthesis is controlled by a stable template and that the regenerating cilia are formed from a pool of ciliary proteins. It is suggested that the proteins of the mitotic apparatus and of the ciliamay be related.

Electron microscope studies on eggs of Mytilus edulis

Normal eggs of the bay mussel, Mytilus edulis, centrifuged eggs, eggs treated with sperm extract, plasmolyzed eggs, and homogenates of whole eggs, were surveyed by electron microscopy. Microvilli increase the egg surface area about fifteenfold. They extend through the vitelline membrane, and delicate fibrils extend from their tips into a jelly coat. Hypertonic sea water detaches the microvilli from the egg and they are retained in the vitelline membrane. Sperm extract causes the vitelline membrane, an intercellular substance, and cortical granules of the cortex to become invisible. The endoplasm of the centrifuged egg stratified into (1) a lipid layer, (2) a clear layer, (3) a mitochondrial layer, and (4) a yolk layer. The constituents of these layers and of the cortex are described. Many of these constituents are recognizable in thin sections of pellets obtained by centrifugation of egg homogenates. The findings are discussed.

Synthetic processes in nucleated and non-nucleated parts of Mytilus eggs

Artificially fertilized eggs of the sea water mussel, Mytilus edulis, were treated with hypertonic sea water and calcium-free sea water in such a way as to cause the polar lobes to constrict off from the remainder of the egg. Batches of eggs from which most of the polar lobes had been removed in this way were allowed to absorb glycine-C-14, adenine-C-14 and methionine-S-35 for a period of 2 1 2 hours. Autoradiographs were then prepared by the stripping film method and the intensity of uptake estimated by counting activity grains above the sections. For all three tracers, separation of the polar lobe cytoplasm from the nucleated part of the cell led to a considerable decrease in the incorporation of these substances into insoluble materials. In a small series of observations no evidence was found that the polar lobe material has a lower rate of incorporation than the rest of the cytoplasm also when it is still attached to the egg. Similarly no difference of uptake was found between complete AB and CD blastomeres.

RESPONSES OF JUVENILE CHUM, PINK, AND COHO SALMON TO SHARP SEA-WATER GRADIENTS

The responses of chum, Oncorhynchus keta (Walbaum), and pink, O. gorbuscha (Walbaum), salmon fry, and coho, O. kisutch (Walbaum), salmon fry and smolts to sea water were studied in sharp-gradient tanks. Chum and pink fry responded positively to isotonic and hypertonic solutions of sea water, but coho fry only to the former. During parr–smolt transformation, coho responded positively to hypertonic sea water. Responses of chum fry acclimated to sea water for 24 hours prior to observation were comparable in intensity to those of unacclimated fry, but less rapid. Activity of acclimated fry decreased less rapidly than did that of unacclimated fry. Fresh water control experiments indicated the presence of some factor or factors which resulted in preferences for "recognized" areas. The effects of positive responses to increased salinity are discussed in relation to the migratory movement of these species from fresh water into the sea.

チチブ Tridentiger obscurus T. et S. の塩分適応能力いついて-I

1. Excepting the cold season, the adaptability for salt solution of a brakish goby Tridentiger obscurus cannot be correctly experimented because of such conditions as higher temperature of the water, maturity of gonad, acceleration of metabolisms, and others. Following results were obtained February to March, 1955 (water temperature, 10°C about). 2. In hypertonic sea water at 1.30-to 1.95-fold of normal its obtained by adding the 4.0-fold Lyman-Fleming artificial sea water, the relation between chlormity and survival time in direct transfering to hypertonic sea water from fresh water, in where fish were landlocked, is shown by the formula “W=aT ?? ” where W is chlorinity in g/L; T time in minute; a. b constant. In hypertonic sea water (at 1. 15-to 4.0-fold), their mortality is 100 per cent at end of experiments after 2.5 days. 3. In the cases of direct transfer to normal sea water or hypotonic sea water from fresh water, and to fresh water or hypotonic sea water from normal its, their mortality is 0 per cent. From these results, the chlorine concentration for survival limit seems to be the chlorinity of normal sea water or a certain one between normal sea water and 1.15-fold of its. 4. This goby could be adapted in the sea water concentrated slowly up to 1.2-fold after three months and to 1.55-fold after four months.

The action of certain polysaccharides on fertilization in the sea urchin egg

1. 1. Several polysaccharides were tested for their action on fertilization in the eggs of Arbacia punctulata and Echinarachnius parma. 2. 2. One sample of heparin (from Hynson, Westcott, and Dunning Co.); a mucopolysaccharide, the human H substance, extracted from pig mucin; and “fucoidin,” a polysaccharide preparation from Fucus vesiculosis, inhibited elevation of the fertilization membrane in relatively low concentrations. Heparin from the Upjohn Co. and also from the Vitrum Co. were relatively inactive. Heating the solutions of Upjohn and Vitrum heparin increased their activity. Oxidation of these polysaccharides with appropriate concentrations of sodium periodate removed their inhibiting activity. 3. 3. Using Hynson, Westcott, and Dunning heparin and Arbacia punctulata eggs the following information was obtained: a) 0.2 per cent heparin prevents cleavage if the eggs are fertilized in the heparin solution. b) If the eggs are fertilized in sea water and then placed in 0.2 percent heparin three to five minutes after fertilization, cleavage occurs. This is true also if the fertilization membrane and hyaline layer are removed to allow penetration of the heparin to the fertilized egg surface. c) Heparin inhibits membrane elevation in eggs from which the jelly coats have been removed. d) Heparin inhibits the membrane elevation which normally occurs when Arbacia punctulata eggs are activated with hypertonic sea water. These results are interpreted as an indication that heparin can prevent cleavage by inhibiting normal fertilization. Also, the heparin has, at least in part, an action on the protoplasmic surface of the egg. 4. 4. Possible chemical mechanisms which might explain the inhibiting activity of heparin are discussed.

On the acid formation, breakdown of cytoplasmic inclusions, and increased viscosity in Paracentrotus egg homogenates after the addition of calcium

1. 1. In fresh Paracentrotus egg homogenates a rapid acid formation was found after the addition of small concentrations of CaCl 2. At the same time certain cytoplasmic inclusions swelled and were more or less completely broken down. The viscosity of the homogenates increased 100–200 per cent. 2. 2. The acid formation was most likely due not only to an incorporation of Ca ++ ions into complexes with acid groups in the homogenate. It was not supposed to be caused by carbohydrate metabolites. An acid formation very similar to the calcium-produced acid formation was caused by papain. A breakdown of certain cytoplasmic granules, and an increased viscosity was observed also under the influence of papain. The calcium effects mentioned above could not be superimposed on the papain effects. 3. 3. Isolated cytoplasmic granules, resuspended in isotonic, Ca-free Bialaszewicz solution of KCl, were no longer influenced by calcium. Calcium is therefore supposed to act through a factor in the cell fluid. As a working hypothesis, this factor is considered to be identical with the acid-producing factor and possibly of enzymatic nature. 4. 4. The acid formation under the influence of calcium is one constituent of the complex acid formation, which was found by Runnström (19) to occur in whole sea urchin eggs in hypertonic sea water.

The Sensitivity of Barnacles and Their Larvae to Copper and Mercury

ABSTRACT Experiments on the toxic effects of copper and of mercury on various stages in the life history, nauplii, cyprids, metamorphosing cyprids and adults of acorn barnacles are described. Most of the work has been carried out on the appropriate stages of Balanus balanoides, but it has been supplemented, wherever possible, by parallel experiments using B. crenatus. Cupric sulphate and mercuric chloride solutions were used as sources of the poisons, and the actual concentration of poison present was determined at the end of each experiment. The period of exposure to the poison was usually 6 hr. A sharp decrease in sensitivity occurs, both in B. balanoides and B. crenatus, between the last naupliar stage and the cyprid. The relative sensitivity of the cyprid of B. balanoides to copper and to mercury is similar to that of the sixth stage nauplius, but the cyprid of B. crenatus is particularly insensitive to copper, but is more sensitive to mercury than that of B. balanoides. Cyprids of B. balanoides only settle in the laboratory some 4 or 5 days after being taken in the plankton and during this period the sensitivity to copper and mercury increases. Settlement can be prevented by very low concentrations of copper and mercury, even though there are no obvious lethal effects. The cyprid of B. crenatus settles more readily in the laboratory, and little change in sensitivity seems to occur during the short interval between catching and settlement. Metamorphosis of the cyprid of either B. balanoides or B. crenatus cannot be prevented by the concentrations of copper (up to 7 mg./l.) possible in sea water. This means that another sharp change in sensitivity occurs after the cyprid of the former species has settled but, because of the low sensitivity of the free-swimming cyprid of B. crenatus, such a change has not been detected for this species. The young barnacle of both species immediately after metamorphosis is much more sensitive to copper than the metamorphosing cyprid. For B. balanoides the sensitivity, both to this poison and to mercury does not change significantly as the barnacle grows, but a small specimen of B. crenatus (less than one month old) is appreciably less sensitive, both to copper and to mercury, than slightly older individuals. Copper and mercury appear to be roughly equi-toxic to the adult of B. balanoides ; the adult B. crenatus is slightly more sensitive to copper and distinctly less sensitive to mercury than that of B. balanoides. In view of these differences in sensitivity of the various stages in the life history of two closely related species, the results obtained with one species should not be held to apply to other species of barnacles. A number of other experiments were carried out using the free-swimming cyprids of B. balanoides. Diluted sea water, though it has no toxic effect in itself over short exposure periods, markedly reduces the toxicity of both copper and mercury. Hypertonic sea water also reduces the toxicity of copper. The sensitivity of these larvae to either copper or mercury is not affected by the presence of sodium oleate. Exposure of these larvae to a wide range of copper concentrations in artificial sea water reveals certain anomalies which may be important in explaining the results obtained when they are exposed to mixtures of copper and mercury in natural sea water. The toxic effect of mercury seems to be similar in either natural or artificial sea water.

THE BEHAVIOR AND METAMORPHOSIS OF THE LARVA OF BUGULA NERITINA (LINNAEUS): EXPERIMENTAL MODIFICATION OF THE LENGTH OF THE FREE-SWIMMING PERIOD AND THE RESPONSES OF THE LARVAE TO LIGHT AND GRAVITY

1. The distribution, external morphology, swimming movements and metamorphosis of the larvae of B. neritina are discussed. During metamorphosis the eye-spots of the larva function in orientation to light. 2. At room temperature (26-30° C.) the larvae under laboratory conditions are geonegative and photopositive during the larval period. Just before metamorphosis they lose their intense positive reaction to light and become more or less indifferent. 3. A reduction of temperature causes larvae to become geopositive and simultaneously prolongs their free-swimming period. When either ascending or descending gradients of temperature are employed, the greater number of larvae change their responses to gravity between 20 and 23.5° C. 4. In cold water (7 to 10° C.) larvae lose their intense positive response to light and become more or less indifferent. Their behavior at reduced temperatures shows that they may become geopositive without exhibiting a simultaneous negative reaction to light. Their descent to the bottom of a vial is not caused by a negative phototropism. Either of the two tropisms may be independent of the other. 5. Larvae made geopositive by a reduction in temperature do not swim upwards towards a source of illumination, when the rays can enter a vial only from above. Neither do they react negatively to light, when the rays enter only from below. Their positive geotaxis cannot be modified by light. At room temperature, however, approximately half the larvae, originally geonegative, swim downwards towards a source of light placed beneath a vial. 6. At 28-30° C. the geotaxis of the larvae is not affected by rapid changes in light intensity. 7. At room temperature, intense light (sunlight and artificial illumination) has some effect in driving larvae to the bottom of a vial. 8. When larvae are returned to diffuse daylight after a 30-minute period in darkness, they do not change either their phototropism or their geotaxis, when they are maintained at low (7-8° C.) or high (26-30° C.) temperatures. Darkness, however, probably reduces their activity and shortens the larval period. 9. A reduction (40-50 per cent) of the salt content of sea water greatly prolongs the natatory period and causes larvae to become geonegative after a long period of swimming at the surface. Hypertonic sea water, however, greatly reduces the free-swimming period, induces a more rapid onset of metamorphosis and causes the larvae to become geopositive. The development of larvae that metamorphosed in sea water of various salinities is discussed. 10. A slight increase in the osmotic pressure of diluted (50 per cent) sea water by the addition of a non-electrolyte does not cause the same response as a similar increase in salt content. 11. An excess of either sodium or potassium causes a rapid loss of pigment. Potassium has the more pronounced effect. Sodium induces a rapid onset of metamorphosis, but potassium does not. Both sodium and potassium cause rapid sedimentation of larvae. 12. A similar excess of calcium greatly prolongs swimming movements and inhibits metamorphosis. An excess of magnesium inhibits metamorphosis, but does not cause prolonged swimming. 13. Mechanical agitation, hypotonic sea water and calcium apparently bring about a positive geotaxis by abnormally prolonging the free-swimming period of the larvae. 14. A tentative explanation of geotaxis in these organisms and a discussion of the effects of various factors on their metamorphosis are presented.

RATE OF BREAKING AND SIZE OF THE "HALVES" OF THE ARBACIA PUNCTULATA EGG WHEN CENTRIFUGED IN HYPO- AND HYPERTONIC SEA WATER

1. Arbacia punctulata eggs, when centrifuged with a force of 10,000 x g, break less readily in hypotonic sea water, and more readily in hypertonic sea water than in normal sea water. 2. When broken apart in hypotonic sea water, the white half is very much larger than the red half. The white half is much larger than the white half obtained by centrifuging in normal sea water, the red half only slightly larger than the red half obtained in normal sea water. 3. When broken apart in hypertonic sea water, the white and red halves are of almost equal size, the white half usually a little smaller than the red half. When broken apart in normal sea water, the white half is somewhat larger than the red half. The white half from the hypertonic sea water is much smaller than the white half from normal sea water, the red half nearly the same size. 4. When the halves obtained by centrifuging in hypotonic sea water are returned to normal sea water, they both lose water, but the white half to a much greater extent than the red half. They become of approximately the same size as though they had been centrifuged in normal sea water. 5. When the halves obtained by centrifuging in hypertonic sea water are returned to normal sea water, they both take up water to about the same extent. The white half remains considerably smaller than when centrifuged in normal sea water. 6. The nucleus of the mature unfertilized egg increases perceptibly in hypotonic sea water and decreases in hypertonic sea water, to a greater percentage volume than the egg itself. It attains normal size on return to sea water.

STABILIZATION OF SPIDER CRAB NERVE MEMBRANES BY ALKALINE EARTHS, AS MANIFESTED IN RESTING POTENTIAL MEASUREMENTS

1. The alkaline earths, Ba, Sr, Ca, and Mg, in isotonic solutions of their chlorides, have, in general, no effect upon the resting potential of non-medullated spider crab nerve. 2. Ba, Sr, and Ca can, however, prevent the depressing action of K upon the resting potential. The order of effectiveness of these ions in this regard is the following: Ba > Sr > Ca. 3. Ba, Sr, Ca, and Mg oppose the depressing action of veratrine sulfate upon the resting potential. The order of effectiveness is Ba > Sr > Ca > Mg. The relation between drop in potential caused by veratrine sulfate and the logarithm of the veratrine sulfate concentration is a linear one. 4. The action of various other organic ions and molecules which depress the resting potential: saponin, amyl urethane, chloral hydrate, and Na salicylate is neutralized by Ba. 5. Hypertonic sea water solutions do not affect the resting potential. Also, preliminary experiments indicate that the nerves do not shrink in hypertonic solutions although they swell in hypotonic sea water. 6. The alkaline earths depress excitability reversibly. The various organic agents which depress the resting potential also depress excitability, in most cases, reversibly, but the concentrations necessary to depress excitability are much smaller than those necessary to depress the resting potential. 7. The relation of these findings to theories put forward as possible explanations of resting potential phenomena is considered.

Regulation of the Haemolymph in the Saline Water Mosquito Larva Aedes Detritus Edw

ABSTRACT The larvae of the mosquito Aedes detritus have been reported only from definitely saline waters. They have been found in water of salinity equivalent to c. 10 % NaCl. In the laboratory they were acclimatized with ease to distilled water, sea water (7 % NaCl), 3 ·5 % NaCl, and glycerol (3 ·5 % NaCl). They also show considerable resistance to N/20 NaOH, but less to N/20 KOH and N/50 HC1. They are unable to live permanently in solutions of the chlorides of potassium, calcium and magnesium of osmotic pressure equivalent to 3 ·5 % NaCl. In sea water of varying salinity they can regulate both the total osmotic pressure and chloride content of the haemolymph. A rise from nil to 6 ·0 % NaCl in the osmotic pressure of the medium is reflected in an increase of from c. 0 ·8 % to 1 ·4% NaCl in that of the haemolymph. In hypotonic solutions and distilled water much chloride is lost, but this is compensated by an increase in the non-chloride fraction. In hypertonic sea water the rise in osmotic pressure is due to increase in the chloride fraction, the nonchloride fraction remaining constant. From this and from experiments with non-electrolytes it is concluded that the larva is permeable to salts and to molecules as large as glycerol, and that the regulatory mechanism in hypertonic saline is concerned with compensation rather for penetration of salts than for loss of water by osmosis. Ligature experiments suggest that this mechanism is the excretion of salt by the Malpighian tubes, but further proof is required. Salt exchange with the environment takes place via the gut, the body surface being impermeable to salts and water. The larvae are able to concentrate chloride from hypotonic solutions but not as effectively as fresh-water species and only when the chloride content of the medium is a little below that of the haemolymph. The anal gills, as in all salt-water species, are very small and appear to be impermeable to salts and water. It is therefore concluded that they are not the seat of the chloride-absorbing mechanism. The osmotic pressure of the haemolymph is trebled by treatment with glycerol (3 ·5 % NaCl), which must be mainly the result of penetration of glycerol. The larva will however live normally in this, and an important factor in the resistance to abnormal media is therefore the adaptability of the tissues to changes in the concentration and composition of the haemolymph. The increase in the osmotic pressure of the haemolymph induced by hypertonic sea water and glycerol does not alter the amount of fluid in the tracheoles. This is discussed in relation to the possible mechanism for the absorption of the trecheóle fluid.

PARTHENOGENETIC DEVELOPMENT OF THE EGGS AND EGG FRACTIONS OF ARBACIA PUNCTULATA CAUSED BY MONOCHROMATIC ULTRAVIOLET RADIATION

1. Ultra-violet radiation either by the full arc for 1/10 to 10 seconds or by monochromatic radiation of 2260-2480A for two to eight minutes causes activation in normal unfertilized eggs of Arbacia punctulata, in the centrifuged whole eggs and in the halves and quarters derived from the whole eggs by centrifugal force. 2. Cleavages of the eggs and fractions have been obtained up to a 12- to 16-cell stage. 3. The nuclear phenomena of the nucleate eggs seem to be normal for the first cleavage, but in later cleavages many abnormal mitoses occur, chiefly multipolar and anastral. 4. Fractions of eggs without nuclei are activated by ultra-violet radiation just as they are by hypertonic sea water. These parthenogenetic merogones cleave and go to a 12-cell stage quite similar to that of a nucleate egg. 5. The ultra-violet radiation affects, therefore, primarily the cytoplasm.

THE ACCUMULATION OF ELECTROLYTES

When cells of Valonia macrophysa were placed in hypertonic sea water, the concentration of halide and of nitrate increased, and the sum of halide + nitrate became 0.05 M greater inside than outside, which is about the same difference as is found in cells in normal sea water. In ordinary sea water the ratio of halide to nitrate is 80,000 to 1. When this was changed by substituting nitrate for halide so that the concentration of halide was 1.75 times that of nitrate the rate of entrance of halide was 1.68 times that of nitrate in 276 hours and the ratio of halide to nitrate in the sap decreased from 38 to 18.5. No halide came out in exchange for entering nitrate. The retention of chloride may well be due to the fact that even when the halide concentration of the sea water is reduced as low as 0.4 M, there is still an inwardly directed activity gradient of sodium chloride.