426 Mr. H. J. Carter on the Reproduction of Sponges. 



Annals, 1863, vol. xii. pi. 3, on Amoeba princeps) — that is, 

 without the nucleus. This cell, again, is exactly like that 

 which I have described and figured as existing so abundantly 

 in Dercitus niger and SteUetta aspera (Annals, 1871, vol. vii. 

 p. 13, pi. 4), and which therefore now must be regarded as ova. 



From the condition of the ovule imbedded in the sarcode, 

 as just described, we go to the seed-like bodies outside it, viz. 

 in the dilated cavities of the excretory canal-system, where 

 they are still pendent to the sarcode by a little pedicle which 

 is analogous to the umbilical cord in higher animals (fig. 14), 

 and which, as the young Tethya becomes fitted for an inde- 

 pendent existence, gradually atrophies until the separation is 

 complete. 



Here, although there is every stage to be observed between 

 the least and most advanced ovule in this part of their deve- 

 lopment, we shall find it convenient to divide them into two 

 groups, viz. that in which the ovule is elliptical, compressed, 

 pear-shaped, and circumscribed by a kind of capsular cover- 

 ing (figs. 14, hhhj and 6 & 12), and that in which it assumes 

 a globular form, with undefined spiculiferous border and 

 areolar sarcode (figs. 14, a a, and 4 & 11). 



In the first instance (figs. 6 & 12) the cellules of the ovule 

 appear to have become broken down into a granuliferous ho- 

 mogeneous sarcode (c) charged Avitli minute refractive silicified 

 spheres, which may be the germs of the spicules that are sub- 

 sequently to appear in the centre of the mass. Those that are 

 now present are all acerate (that is, without heads), and do not 

 reach the confines of the ovule (fig. 5) — which presents a de- 

 fined margin (a) with the shape above mentioned, and in this 

 form is attached to the dilated cavity of the excretory canal- 

 system by the little pedicle mentioned. 



In the second instance (figs. 4 & 11) the " granuliferous ho- 

 mogeneous sarcode " has become areolar (a) ; the spicules have 

 greatly increased in number [h) ; heads of different shapes 

 have been and are being added to them ; they have burst 

 through the defined margin of the foregoing development, and 

 carried out with them the areolar sarcode into a papillated 

 globular form, in miniature, like that of the parent. Young 

 sponge-animals have in all probability begun to grow in the 

 areolar cavities ; and the pedicle of attachment perishing, the 

 little sponge falls loose into the excretory canal-system, through 

 which it is rapidly ejected into its new element, there to find 

 a place of attachment (perhaps again the stem of a Halichon- 

 dria ventilabrum) and finally attain its adult size. 



These two descriptions apply to the ovules of Tethya 

 cranium as well as to those of T. zetlandica ; only the spi- 



