Different Classes Of Vertebrates Research Articles

SEX CHROMOSOMES IN AMNIOTA

During the past 25 years the chromnosomal conditions in Vertebrates have been the subject of a great many investigations. With some justification it has been hoped that such work might add to our present knowledge of the evolutionary relation between the different classes of Vertebrates and, in this connection, special attention has been given to the sex chromosomes. Unfortunately the findings of various cytologists are by no means in agreement and the present note represents an effort to reach a final conclusion, at least so far as the Amniota are concerned. The case of the Anamnia is much clearer: with the only exception of the fish Mogrunda obscura where Nogusa (1955) has described in the male a heteromorphic bivalent of the X-Y type, we may assert that, as a rule, there is no cytological expression of the digamety in Fishes and Amphibians (Matthey, 1949). Application of a modification of Makino and Nishimura's (1952) squash technique to all major groups of the Amniotca, except for the Rhynchocephalia, has led us to the following conclusions:

Modes of Gastrulation in Vertebrates

ABSTRACT The modes of gastrulation in the different classes of Vertebrates are discussed from a comparative point of view, with the particular aim of finding some system which avoids postulating a sharp dualism between the anamniote telolecithal forms, in which the edge of the blastoderm consists of presumptive endoderm, and those of the Amniotes, in which it is ectodermal. It is suggested that the most profitable way of regarding all blastodermic forms is to envisage them as derived from the basic type of blastula by a process in which the roof and floor are squeezed together, so that a flatfish double-layered plate is produced. The concept of the ‘primitive edge’ of such a blastoderm is introduced, and it is suggested that in the amniotes the presumptive ectoderm has expanded greatly beyond the primitive edge, while there has also been a strong convergence towards the dorsal side. The conditions in certain highly yolky amphibian eggs are shortly described, and it is argued that they show conditions similar to those which would be expected on the hypothesis of a squeezing together of the blastula roof and floor.

Morphologic instability of central synapses

In the tissues of animals of normal appearance belonging to very different classes of vertebrates, both fishes and mammals, I have observed destructive phenomena in the finest neural terminations, the metaterminal apparatus. These phenomena are manifested through the production of tiny accumulations of a silver-staining substance, or rather by the formation of a tiny round plaque (rondelle) characteristic of an abortive regeneration. In the anterior nucleus of the thalamus of the adult rabbit, these processes are localized in minute islets, within which they can be observed equally well on the pericellular terminations and on the terminations of the neuropil. When these synaptic alterations are at their maximum, the nervous impulses are without, profoundly modified, or even interrupted.

Structures Developed in Amphibians by Implantation of Living Fish Organizer

The study of mutual interactions between developing fish and amphibian tissue was tested by implanting parts of fish blastulae into the blastocœle of developing amphibians. This method applies also to the study of the capacity for differentiation of isolated embryonic cells of the teleostean. Halves of blastulae of the eggs of Danio rerio (the Zebra fish), isolated from their yolk an hour before the commencement of the visible processes of gastrulation, were implanted into the blastocœle of Triturus torosus eggs. The hosts were fixed after 10 days of development.The developing fish and amphibian cells are mutually compatible during gastrulation and the stages immediately following. Thus developing tissue of young embryos from different classes of vertebrates at first possess considerable tolerance, even though a marked tissue specificity characterizes the adults. In the present series of experiments, the implanted fish material developed wherever located: in the center of the yolk, between yolk and epidermi...

THE REACTION OF THE ERYTHROCYTES OF VERTEBRATES, ESPECIALLY FISHES, TO VITAL DYES

The reactions of the mature erythrocytes of seventeen species of fishes to the vital dyes neutral red, Janus green B, and brilliant cresyl blue, have been studied. In most teleosts the primary vital granules are readily demonstrated by neutral red and consist of one or two small granules eccentrically placed near one pole of the nucleus, but in the menhaden, alewife, and mackerel the primary granules are most numerous and are either arranged in a single definite line about the nucleus or scattered irregularly throughout the cytoplasm. In the elasmobranchs the granules are large, numerous, and scattered. In a majority of the teleosts the primary granules may be demonstrated as basophilic bodies in dry films stained by Wright's method and are also frequently seen in fresh unstained preparations.Secondary or induced granules may also appear in the cytoplasm of cells exposed for long periods to the dye. The degree of induction of new bodies does not appear to depend entirely on external factors but is determined to a large extent by factors inherent in the cytoplasm of the given species. In general the mitochondria are filamentous, reduced in number, and lie in chose contact with the surface of the nucleus.The reticular substance in all mature erythrocytes of the fishes is greatly reduced and appears either as short irregular filaments or as minute granular remnants. It is best demonstrated with brilliant cresyl blue.An attempt is made to compare the relative degree of differentiation attained by the mature erythrocytes of the several classes of vertebrates. The following criteria have been considered: changes in nuclear-cytoplasmic ratio; chromatin distribution in the nucleus; involution of the nucleoli; loss of basophilia; changes in the form, distribution, and volume of mitochondrial substance; reduction of reticular substance; amount of primary granules; and degree of induction of secondary granules. Of these criteria the degree of persistence of reticulation has been found to be the most consistent, and on this basis the several classes of vertebrates are arranged in the following ascending order of relative differentiation attained by their erythrocytes at maturity: amphibians, reptiles, fishes, birds, and mammals. This arrangement is also supported by the behavior of the nucleoli, which persist in the erythrocytes f amphibians and reptiles but are not usually demonstrated in the mature cells of fishes and birds.The history of the primary and secondary granules is less regular and consequently less useful for measuring the relative differentiation attained by the cells of different classes of vertebrates. However, within a given class of vertebrates it is concluded that the presence of a large number of primary granules or the rapid induction of new granules in mature cells may be regarded as supplementary evidence of a lesser degree of differentiation. The presence of primary granules or the degree of induction of new granules, however, cannot always be correlated with the degree of persistence of reticulation.It is also concluded on the basis of this survey of the vertebrate erythrocyte that primary granules, secondary granules, and patterns of reticulation as revealed by vital dyes, must be regarded as three separate entities which are not genetically related.

A contribution on the minute anatomy of the sympathetic ganglia of the different classes of vertebrates

Journal of MorphologyVolume 16, Issue 1 p. 27-90 Research Article A contribution on the minute anatomy of the sympathetic ganglia of the different classes of vertebrates G. Carl Huber, G. Carl HuberSearch for more papers by this author G. Carl Huber, G. Carl HuberSearch for more papers by this author First published: November 1899 https://doi.org/10.1002/jmor.1050160103Citations: 47AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume16, Issue1November 1899Pages 27-90 RelatedInformation