No. 3.] NOTES ON DEVELOPMENT OF SOME SPONGES. 5 19 



My observation that layers similar to germ layers are de- 

 veloped 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 construction 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, germinal layers in the buds of 

 Loxosoma, and emphasized the biological significance of the 

 phenomenon. 



In his paper " Zur Orientirung iiber die Entwicklung der 

 Schwamme {Zeit. f. 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 (1) this must 

 have seemed a remarkable statement, and it would be interest- 

 ing to know if the observations which led Professor Schmidt 

 to this view were not made on a gemmule development resem- 

 bling that which I have described. 



University of North Carolina, 



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



PAPERS REFERRED TO. 



Barrois. Mdmoire sur l'embryologie de quelques Eponges de la Manche. 



Ann. d. Set. Nat. 1876. 

 Marshall. Die Ontogenie von Reniera filigrana. Zeit.f.w.Z. 1882. 

 Keller. Studien iiber die Organisation und Entwicklung der Chalineen. 



Zeit.f. w. Z. 1880. 

 Schmidt, Oscar. Zur Orientirung iiber die Entwicklung der Schwamme. 



Zeit.f. w. Z. 1875. 

 Fiedler. Ueber Ei und Samenbildung bei Spongilla fluviatilis. Zeit.f. 



w. Z. 1888. 

 Dezso. Die Histologie und Sprossenentwicklung der Tethyen. Archiv 



Mikr. Anat., Bd. 16 and 17. 1879 and 1880. 



