31 



what happens in Grantia. The later differentiation of the embryo 

 into cohminar and granular cells is accounted for by the absorp- 

 tion by the latter of increased quantities of food necessary for the 

 free Hfe of the larva. Also if we look upon the formation of the 

 pseudogastrula as due to physical causes only, its presence offers 

 no obstacles to this view. 



If it is correct that the sponge larva settles down by, and 

 becomes invaginated at, the animal pole, this removes the supposed 

 homology between it and the embryo of the Coelenterates, the only 

 other group to which it is possible to trace a relationship, and 

 suggests rather that the two groups have originated quite inde- 

 pendently. 



This would make it fairly certain that Grantia and the other 

 similar forms reproduced from choanocytes are not far removed 

 from the colonial Choanoflagellates, and are much more closely 

 allied to these than to any other known forms in the animal 

 kingdom. 



LIST OF LITERATURE REFERRED TO. 



1. Dendy, A, " Observations on the Gametogenesis of Grantia compressa.''' 



Quart. Journ. Micro. Sci., vol. 60, N.S., 1914. 



2. Dendy, A. " On the Pseudogastrula Stage in the Development of Cal- 



careous Sponges." Proe. R.S. Victoria, 1890. 



3. Dendy, A. " Studies in the Comparative Anatomv of Sponges, 111." 



Quart. Journ. Micro. Sci., vol. 32, N.S., 1891. 



4. Minchin. " Porifera," in Lankester's " Treatise on Zoology," vol. 1. 



5. Carter, J. H. " Notes introductory to the Study and Classification of 



the Spongida." Ann. and Mag. Nat. Hist. 



6. Saville-Kcnt, J. " A Monograph of the Infusoria," vol. 1, p. 143. 



