264 ANATOMY AND PHYSIOLOGY 



FIG. 



. CYLINDRICAL : ENTIRELY SPINED ; SPINES OF THE 

 MIDDLE CYLINDRICAL, THOSE OF THE TERMINATIONS 

 CONICAL AND RECURVED. These spicula might 

 readily be mistaken by a hasty observer for those 

 of Spongilla alba, but a closer observation exhibits 

 essential differences in their mode of spination. 

 They are very numerous in the envelope of the 

 ovary of Spongilla cinerea, Carter, from the water- 

 tanks of Bombay. They are so nearly of the same 

 form as those represented by Fig. 207, as to render 

 it unnecessary to figure them. Page 59. 



2ND. SPICULA DISPOSED IN LINES RADIATING FROM THE 



CENTRE TO THE CIRCUMFERENCE OF THE OVARY. 



Birotulate and Boletiform Spicula. 



208. ADULT RECURVO-DENTATE BIROTULATE SPICULUM. 



Shaft entirely spined, from the ovary of Spongilla 

 plumosa, Carter. X 660 linear. Pages 59 

 61. 



209. A view of the inner surface of one of the rotulae of 



the spiculum represented by Fig. 208, showing the 

 amount and irregularity of the dentation of its 

 margin. X 660 linear. 



210. First stage of development of a birotulate spiculum 



from :the ovary of Spongillaplumosa, Carter. X 660 

 linear. Page 61. 



211. Second stage of development of a birotulate spiculum 



from the ovary of Spongillaplumosa, Carter. X 660 

 linear. Page 61. 



212. Third stage of develepment of a birotulate spiculum 



from the ovary of Spongillaplumosa, Carter. X 660 

 linear. Page 61. 



