I04 JOURNAI, OF THE 



chromatin is visible. The maturation of the egg in these 

 two sponges is seen to be very like that of Spongilla, as 

 described by Fiedler (5). Fiedler regards the two chroma- 

 tin balls as polar bodies; but as an objection to this view it 

 must be urged that they are formed (though not dis- 

 charged) long before the egg has reached its full size. 



My observation that layers similar to germ layers are 

 developed in the asexual embryos of certain sponges recalls 

 the account given by Dezso (6), of the formation of buds in 

 Tethya. Dezso claims that these buds develop from single 

 cells, and that in them germ layers are formed. The con- 

 struction he puts upon certain cells seems, however, an 

 arbitrary one, and I find it difficult to carry out a detailed 

 comparison between his observations and my own. Oscar 

 Schmidt, as Dezso calls to mind, described in 1878, germi- 

 nal layers in the buds of Loxosoma, and emphasized the 

 biological significance of the phenomenon. 



In his paper, " Zur Orientirung iiber die Etwicklung 

 der Schwiimme" (Zei'L /. w. Z, 1875), Oscar Schmidt 

 makes the statement that in the silicious (and horny) 

 sponges there is no true segmentation, the ovum very 

 early losing its cellular character. To many others 

 besides Barrois (i) this must have seemed a remarkable 

 statement, and it would be interesting to know if the 

 observations which led Professor Schmidt to this view 

 were not made on a gemmule development resembling 

 that which I have described.* 



University of North Carolina, 



Chapel Hill, N. C, October 17, 1891. 



PAPERS REFERRED TO. 



1. BarroIvS. Memoire siir I'enibo'ologie de quelques Eponges de la 



Manche. Ann. d. Sci. Nat. 1876. 



2. Marsh ALi^. Die Ontogenie von Reiniera filigraiia. Zeit. f. w. Z. 



1882. 



