202 KINGSLEY AND CONN 



which is not warranted without considerable qualification. It must be understood that I 

 am not criticising his observations on the free cell formation in the intermediary layer and 

 in the yolk, nor do I deny that a portion of the hypoblast may arise from those portions. 

 This free cell formation we have both witnesed in the eggs of several marine Teleosts and 

 we are willing to accept his account of their formation but I do deny that the presence of 

 these cells and nuclei can be addressed as evidence that the deutoplasmic globe itself can 

 be considered as a cell and the complete homologue of the hypoblast. On p. 56 he con- 

 siders that the hypoblast described by Haeckel, and which closely resembles in its structure 

 and mode of origin that of our fishes, was in reality " composed of cells derived from the 

 intermediary layer." It hardly seems possible that there should be in the eggs of teleosts 

 such diverse methods of origin of the hypoblast and that in closely allied forms. Profes- 

 sor Van Beneden following Haeckel regards his egg as probably belonging to one of the 

 Gadidae, and with this opinion we are inclined to agree. The eggs of Merlucius and of 

 Morrhua present a striking resemblance to those studied by Haeckel and Van Beneden, 

 and if there be any relation between the characters of the eggs and of the fishes produc- 

 ing them (a point on which we have but slight data) the eggs studied by both probably 

 belonged to the Gadidae. Now as we have observed in an egg with a conspicuous oil globule, 

 and as has been traced through with great care by our friend Mr. Van Vleck in the egg 

 of Merlucius, the hypoblast arises exactly as we have described it above. 



It would thus appear that Van Beneden has been led into an error either of observation 

 on his own eggs, or of interpretation of the results of Haeckel, regarding this jjoint and we 

 are inclined to believe that the former is the case, for the reason that it appears from inter- 

 nal evidence presented by the article in question that he did not witness continuously the 

 phenomena presented by his eggs. Still there remain certain statements which we can- 

 not reconcile with what we believe to be the facts of the case. For instance the statement 

 on p. 5G. " The blastodisc remains all this time very sharply delimited inferiorly and in 

 no part is there a passage from one to the other (from the upper portion of the blastoderm 

 to the hypoblast). In no part have I found the slightest indication in favor of 

 invagination." 



In the earliest stages of the egg the intermediary layer is not present but it soon appears 

 and acquires its maximum development about the time of invagination. It appears to 

 arise by an elaboration' of the food yolk into protoplasm. It consists in our eggs as in those 

 of Van Bambeke and Van Beneden of a thin layer extending across the egg between the 

 blastoderm and the food yolk, and having a thickened marginal welt. This welt extends 

 down some distance over the yolk and it may be possible that the nuclei of the yolk men- 

 tioned on p. 199 belong in reality to this extension of this layer. Klein ('72) describes this 

 as a ring in the trout as he failed to find the portion extending across between the blasto- 

 derm and yolk. 



Most observers have considered the mesoblast as arising as a continuous sheet in the 

 Teleosts but Calberla claims that it is in two halves as in the Elasmobranchs. 



We found no traces of the segmentation cavity of Van Bambeke and judging from the 

 irregularity of his figures we are inclined with others to regard it as a product of reagents 

 or the section knife. The segmentation cavity of Von Baer which was found in our eggs 

 is clearly homologous with that of other forms of animals. 



