OF THE SPONGIADJE. 143 



species common on the rocks in the neighbourhood of 

 Torquay, and which I described in a paper read before the 

 Microscopical Society of London in 1841, these organs 

 assume an oval form ; they are also considerably depressed. 

 In a young specimen of this species of sponge in my pos- 

 session, the progressive development of the ovaria is very 

 strikingly illustrated. Fig. 330, Plate XXIV, represents 

 an adult ovarium. Fig. 331, one in a semideveloped state, 

 and Fig. 332, one of the same organs in a very early stage 

 of development. In another species of sponge from the 

 South Seas we find a singular variety of this class of 

 ovarium. It is oval in form, the length being to the breadth 

 as five to three, but it is so much depressed as to appear 

 rather like a dermal spicular plate than an ovarium ; but the 

 radiate arrangement of its component spicula is perfectly 

 visible with a power of 666 linear, and their distal termi- 

 nations as separate and distinct as those of Geodia or 

 Pachymatisma. The situation of the foramen is also well 

 defined in many of them. Fig. 333, Plate XXIV, represents 

 a mature ovarium ; Fig. 334, a fragment of one to exhibit 

 its degree of thickness; and Fig. 335 represents one of the 

 same species of ovarium in an early stage of development. 

 I have seen four species of sponge which have this descrip- 

 tion of ovarium ; in one it is very considerably longer in 

 its proportions than that represented by Fig. 333, Plate 

 XXIV, and in another species it is somewhat shorter. 



Since the preceding portion of the account of the ovaria 

 was written I have received a very remarkable specimen of 

 these organs, which differs materially in its structure from 

 any of the forms that I have previously described. The 

 sponge consists of a small portion of basal membrane, closely 

 resembling that of a Halichondraceous species. It was 

 found by my friend Mr. J. Yate Johnson coating rocks 

 and stones at Madeira. The remains of several exhausted 

 ovaria are dispersed over the surface of the membrane, a 

 few only retaining their original form and proportions. 

 They do not appear to have had a spicular skeleton, but to 

 have consisted of a coriaceous envelope strengthened and 

 supported by a reticulated skeleton of apparently keratose 



