36 EMBRYOLOGY 



place. In the following spring the germ-body crawls out hrough the 

 pore, to become attached and metamorphosed into a young sponge, by 

 means of processes of development which have not yet been accurately 

 studied.* 



From what has been said it follows that in the gemmnlee 

 we have to do with an encysted portion of the parent body, 

 provided with food-yolk and retrograded to an embryonic 

 condition, which acquires the power to regenerate the parent 

 organism. On this account gemmulation has also been 

 designated as a kind of internal budding. In support of 

 another current interpretation, according to which the 

 gemmules would represent the winter eggs of Spongilla, 

 evidence is as yet entirely wanting, for in this case it would 

 be necessary to prove that the germ- body originates by the 

 division of a single original cell, but all observations made 

 up to the present time are opposed to this. 



Literature. 



Earlier writings by Geant, Liebeekuhn, and Miclucho-Maclay. 



1. Balfouk, F. M. On the Morphology and Systematic Position of the 



Spongidse. Quart. Jour. Micr. Sci. Vol. xix. 1879. 



2. Baerois, C. Memoire sur I'embryologie de quelques Eponges de la 



Manche. Ann. sci.nat. {8er.4). Tom. iii. 1876. 



3. Cartee, H. J. Development of the Marine Sponges, etc. Ann. and 



Mag. Nat. Hist. Vol. xiv. 1874. 



4. Ganin, M. S. Zur Entwicklung der Spongilla fluviatilis. Zool. 



Anzeiger. Jahrg. i.. No. 9. 1878. 



5. Ganin, M. S. Materialien zur Kenntniss des Baues und der Ent- 



wicklung der Spongien. Warschau. 1879 (Russian). 



6. GoETTE, A. Untersuchungen zur Entwicklungsgeschichte von Spon- 



gilla fluviatilis. Hamburg u. Leipzig. 188Q. Also Zool. Anzeiger. 

 Jahrg. vii. u. viii. 



7. Haeckel, E. Die Kalkschwamme. Berlin. 1872. 



8. Heideb, K. Zur Metamorphose der Oscarella lobularis. Arheiten 



a. d. zool. Inst. z. Wien. Bd. vi. 1886. 



9. Keller, C. Studien iiber die Organisation und die Entwicklung der 



Chalineen. Zeitschr.f. wiss. Zool. Bd. xxxiii. 1880. 

 10. Marshall, W. Die Ontogenie von Reniera filigrana. Zeitschr.f. 

 wiss. Zool. Bd. xxxvii. 1882. 



» [Compare Zykoff (Nos. VIII. and IX., Appendix to Literature on 

 Porifera).] 



