Bibliographical Notices. 5 1 



Chap. III. De I' ceuf feconde et du germe. — Treating of the milt or 

 sperm, M. Vogt writes, " On ne sait cependant presque rien du role 

 que les differentes parties de cette liqueur jouent dans la feconda- 

 tion. Je me suis donne toutes les peines possibles pour savoir com- 

 ment se comportent, dans la fecondation, ces animalcules spermatiques 

 de la palea, mais en vain." The rotatory motion of the vitellus 

 known in the ova of Mollusca, and observed in those of Mammalia 

 by Bischoff, has not been noticed in the ova of the C. palea, which 

 seem on the contrary to remain in the same position, the oily disc 

 being turned upwards. At certain periods after fecundation furrows 

 and small regular elevations are discovered on one side of the ova : 

 M. Vogt observes, " I consider that the ova of fishes are distinguished 

 from those of many other animals, and in particular from those of 

 the frog, inasmuch as these furrows affect only the germ and never 

 the vitellus, and cannot in reality be formed in any other man- 

 ner, since in the egg of the C. palea the vitellus is completely 

 deprived of cellules." And in speaking of the primitive formation 

 of the germ, he concludes with the following sentence, printed in 

 italics : — " Les cellules du germe embryonique se developpent des taches 

 germinatives, que par consequent les taches germinatives sont en re'aliU 

 les ve'ritables cellules embryonaires primitives, et que, dans les poissons, 

 elles forment a elles seules le premier rudiment de I'embryon." 



Chap. IV. Uembryon jusqu'a la fermeture du sillon dorsal. — 

 M. Vogt considers that the true embryonic development does not 

 commence until the divisions of the germ into two parts, the embryo 

 and vitellary vesicle ; previous to this the embryo is only a simple 

 enlargement of the cellules. The first appearance of the embryo 

 takes place under the form of a linear and uniform enlargement of 

 the cellules which form the embryonic substance ; in short, that this 

 " bande primitive " as it is named by M. Baer, exists in fishes as well 

 as in the fowl or birds ; but he does not think with M. Baer that it is 

 the commencement or forerunner of the vertebral column, nor the 

 primitive form of the cerebro- spinal system. The transformation of 

 the cephalic or anterior part of the furrow into many distinct divi- 

 sions is the first index of the central nervous system, composed of 

 the brain and spinal marrow. This transformation is not charac- 

 terized by a new formation of cellules, nor by the appearance of cel- 

 lules of a particular structure. 



Chap. V. Developpement du systeme nerveux central. 



Chap. VI. Developpement des organes des sens. — Speaking of the 

 eye, where, in the embryo of the higher classes, it has been ad- 

 vanced that the two ocular sinuses are at first united, M. Vogt states, 

 that " in fishes at least I can affirm that the ocular sinuses are 

 situate from the commencement upon the sides of the head, deeply 

 separated by the cavity of the mesencephale. Of the ear, the first 

 traces of the auditory organs show themselves when the formation 

 of the crystalline sinus begins to appear in the eye. The nose, or 

 development of smell, appears later than the other organs of the 

 senses. 



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