OF THE SPONGUDiE. 263 



Fig. 



The spination of the spicuhim is very remarkable ; 

 those near the middle of the shaft are frequently of a 

 length equal to half or two-thirds the greatest 

 diameter of the spiculum on which they are based. 

 They are of the same diameter from the base to the 

 apex, and terminate as abruptly as if they had been 

 truncated. Page 38. 



205. ACERATE: ENTIRELY SPINED, SPINES CONICAL. X 



660 linear. ---This form of spiculum occurs in the 

 envelope of the ovary of Spongilla cinered, Carter. 

 It is very abundant and somewhat minute, and re- 

 quires a linear power of about 600 to define it 

 accurately. The spines are very numerous, and 

 all of them appear to pass from the spiculum at 

 right angles to its axis. The largest of them is 

 about one-third the length of the greatest diameter 

 of the spiculum. 



206. Cylindrical : incipientlt spined. X 400 linear. 



— This short stout form of spiculum occurs a.bund- 

 antly in the envelope of Bpongilla gregaria. Bower- 

 bank, from the River Amazon. It is usually with- 

 out spines, but occasionally a few incipient ones 

 are dispersed over the shaft. 



207. Cylindrical: entirely and recurvedly spinous. 



X 400 linear. -^This large and beautiful form of spi- 

 culum is abundant in the envelope of the ovary of 

 Spongilla alba, Carter. It has a considerable 

 aiiioutlt of curvature, and the spination is remark- 

 ably bold and striking. Very fe\^ of the spines 

 issue from the shaft at right angles to its axis, and 

 these are always near its middle ; the remainder of 

 the spines are all curved from the apices of the 

 spiculum towards the middle of the shaft. The 

 spines are congregated in considerable numbers at 

 each termination of the spiculum^ and ai'e larger 

 and more curved there than on any other part of 

 the shaft. 



