402 Miscellaneous. 



have been executed, under the author's superintendence, by Mr. De 

 Wilde and Mr. A. S. Eoord ; and those artists have worked with a 

 zeal and care which really leave little to be desired. With scarcely 

 an exception the figures are most satisfactory ; and we are glad 

 to see that Mr. Foord has succeeded in rivalling the veteran 

 coralliographer with whose work his own is here brought into com- 

 petition. 



MISCELLANEOUS. 



On some Facts in regard to the, first Phenomena of the Development 

 of the Osseous Fishes. By M. L. F. Henneguy. 



The formation of the blastodermic leaves in the osseous fishes is 

 still but little known. In the trout, (Ellacher makes the meso- 

 derm and endoderm originate from the deeper layer of the germinal 

 disk by simple differentiation of cells. According to Kupffer, Van 

 Bambeke, His, and Klein the mesoderm alone results from the 

 differentiation of the deeper layer of the germ, and the endoderm is 

 formed by the cells which originate in the subblastodermic layer of 

 Lereboullet, or the parablast of Klein. Lastly, Gdtte supposes that 

 the blastoderm folds under at the margins to form a layer of cells, 

 which afterwards subdivides into mesoderm and endoderm. 



My own observations in part cenfirm those of Gdtte. Sections 

 effected in germs of trout of from seven to ten days, hardened by 

 osmic acid, have in fact shown me very distinctly the reflection of 

 the blastoderm at its margins. The germ at this epoch is spread 

 out upon the vitellus in the form of a lamina with thickened con- 

 tours, the thinner centre of which conceals a cavity, the germinal 

 cavity. The external surface of the germ is constituted by a layer 

 formed by a single series of cylindrical cells. This layer appears 

 very early, long before the germ begins to spread over the vitellus ; 

 (Ellacher has given it the name of the corneous lamina. Beneath 

 this lamina there is a pericellular layer, presenting at first the 

 same thickness throughout ; this is the sensorial layer. This layer 

 soon becomes inflected at the periphery of the disk, towards the 

 vitellus, and penetrates into the germinal cavity ; the corneous 

 lamina takes no part in this inflexion, and stops suddenly at the 

 surface of the vitellus. In sections made across a germ arrived at 

 this stage of development, we see a linear fissure separate the sen- 

 sorial layer from the reflected portion of the blastoderm and stop 

 at a certain distance from the rounded margin of the germ. 



In germs hardened by chromic acid the fissure is not visible ; in 

 its place one only observes a line separating the two layers of the 

 blastoderm, but stopping at a certain distance from its free margin. 

 This fact explains the opinion of G311acher, who, having hardened all 

 his trout-ova in chromic acid, assumes only a simple differentiation 

 of cells for the mesoderm. 



