On the Development of the Marine Sponges. 321 



first grow inwards into the body-cavity of the planula. It is 

 only just before the escape of the actinuloid from its capsule 

 that they evaginate themselves and become external. 



22. After enjoying for one or two days its free existence, 

 during which it moves about by the aid of its long arms, 

 the embryo fixes itself by its proximal end, the long' arms 

 gradually disappear, the short permanent tentacles increase in 

 number, and the essential form of the adult is soon acquired. 



XXXIX. — Development of the Marine Sponges from the 

 earliest Recognizahle Appearance of the Ovum to the Per- 

 fected Individual. By H. J. Carter, F.R.S. &c. 



[Plates XX., XXI., & XXII.] 



It is now twenty-five years since my figure of the Freshwater 

 Sponges, viz. Spongilla, as it grows out of the so-called " seed- 

 like body," was described and published ('Annals,' 1849, 

 Sept., vol. iv. pi. iv. fig. 2), and seventeen years since the 

 observations and illustrations in my paper " On the Ultimate 

 Structure of Spongilla " were obtained by following this de- 

 velopment ('Annals,' July 1857, vol. xx. p. 21, pi. i.). My 

 military duties at Bombay then compelled me to remain much 

 at home, while in the tanks of the garden about the house 

 where I lived Spongilla grew abundantly ; so that, although I 

 resided for many years at Bombay, and thus on the borders of 

 the sea, I could only make use of the opportunities which the 

 freshwater tanks of the island afforded. 



Time has passed, and I have retired to my native place 

 (Budleigh-Salterton, south coast of Devon), still on the 

 " borders of the sea," but now in Great Britain. The duties 

 of official occupation are over, and I have yet a little time left 

 to study now the physiology of the marine sponges. 



This may explain to those who, like Hackel (' Die Kalk- 

 schwamme,' vol. i. p. 28), express wonder that I should have 

 exclusively studied the freshwater sponges while at Bombay, 

 where there is, too, such a rich sponge-fauna on the " coasts 

 of the Indian Oceans " for this purpose. Had I been a 

 German professor, the matter might have been different, and 

 I might have obtained indulgences in the way of " leave " for 

 studying the marine sponges, which the military authorities 

 at Bombay, if they had been appealed to on this behalf, would 

 have laughed at. 



But to show that while on " the coasts of the Indian 

 Oceans " I did not entirely neglect the marine sponges, it 



