Mr. H. J. Carter on the Reproduction of Sponges, 427 



cules in the former are arranged in a whorl from the com- 

 mencement, and accompanied by the Ibihamate spicule (figs. 11 

 & 12), which points of distinction are, of com*se, absent in the 

 latter. 



It might also be observed that, although the one-armed 

 anchor-headed spicules project beyond the rest in the young 

 Tethyoi of both species, they do so to such an extent in T. 

 cranium as to form a kind of fringe (fig. H, c). 



I am not prepared to make any lengthened comparison 

 between these young Tethyce, and the so-called " seed-like 

 bodies " of Spongilla. At first it would appear that there is 

 not any very great difference between their sizes respectively, 

 the fully developed young Tethyadce of T. cranium and T. 

 zetlandica being respectively l-24th and l-16th of an inch in 

 diameter, while the seed-like bodies of the five species of 

 Spongilla at Bombay, viz. cinerea, Carteri^ alba^ Meyeni^ and 

 pJumosa, average respectively l-63rd, l-29th, l-30th, l-47th, 

 and l-22nd of an inch in diameter, the last measurement being 

 the long diameter of the elliptical form (Annals, 1849, vol. iv. 

 p. 81). But when it is considered that these measurements 

 include the thick crust which surrounds each seed-like body, 

 and that the globule of soft contents is still smaller, that no 

 spicules are yet developed in it, and that it cannot be con- 

 sidered the '' fully developed" young Spongilla until it has 

 left the capsule, it becomes evident that we are not comparing 

 like with like. In short, the state of the contents of the seed- 

 like body much more resembles the ovule of the Tetliyce while 

 " imbedded in the sarcode " (fig. 7) than any other stage of the 

 latter above described. At a very early period the seed-like 

 body of Spongilla very much resembles in all particulars the 

 globular body of the sponge-animalcule itself, somewhat 

 enlarged; and when fully formed, its contents consist of a 

 globular cell containing a number of spherical cellules filled 

 respectively with granular matters, among which are many 

 still smaller cells or germs. Thus it closely resembles in this 

 respect the ovule of the Tethyte before it leaves the sarcode to 

 become pendent in the dilated cavity of the excretory canal- 

 system. Hence it now seems to me that we should regard the 

 so-called seed-like bodies of Spongilla as ti'ue ova, which, like 

 the seeds of plants, are wrapt up in a shell for preservation 

 until such time and circumstances occur as are favourable to 

 their development. As the contents of the seed-like body 

 issue from the capsule, the globular cells and their contents 

 respectively appear to pass directly into the globular groups 

 of sponge-animalcules, and the excretory canal-system to be 

 hollowed out, and tlie horny skeleton and spicules formed, in 



29* 



