350 Mr. H. J. Carter on tJie Beproductive 



dorsal, which is considerably behind the base of the ventrals. 

 Caudal not forked. Pale brown above, with numerous black, 

 spots of unequal size. 



Total length 135 millim.. 



Two specimens. 



XLIV. — On the Reproductive Elements of tJie Spongida.. 

 By H. J. Carter, F.R.S. &c. 



It is not necessary now to question whether the Spongida are 

 propagated by male and female elements of generation,, that 

 is by spermatozoa and ova in tlie usual way, as so many 

 have described and illustrated these elements in different 

 species of the class, beginning as far back at least as 

 1826, when Grant described and delineated the ova in Spongia 

 panicea and S. •papillaris^ now Halichondria incrustans and 

 H. panicea^ Bk. (Edinburgh New Phil. Journ. vol. ii. p. 127 

 &c. pi. ii. fig. 26 &c.), and 1856, when Lieberkiihn de- 

 scribed and illustrated the spermatozoa in Spongilla (Archiv 

 f. Anat. u. Physiol. Heft i. p. 17, and Heft v. p. 500, Taf. 

 xviii. figs. 9 and 10). But still it remains to be pointed out 

 from what parts of the sponge these elements are respec- 

 tively derived. 



Following the discoveries as they were made, let us first 

 direct our attention to the ovum. 



By " ovum '^ I wish to be understood to mean that stage in 

 which this element is chiefly characterized by the presence of 

 the germinal vesicle ; the segmentary stage, that in which it 

 is chiefly characterized by the absence of the germinal vesicle ; 

 and the embryonic state, that in which it is chiefly character- 

 ized by the addition of cilia or motory organs to the surface. 



At the earliest period in which I could detect the ovum (in 

 Halichondria lohularis) it was about l-3000th in. in dia- 

 meter, which was thus but a little larger than the spongozoon 

 (" Geissel-" or " Kragenzell " of the Germans) ; while later 

 on, that is when about 1000th in. in diameter, it presented all 

 the characters of an unimpregnated sponge-ovum — that is^ 

 presenting the germinal vesicle and germinal spot surrounded 

 by a polymorphic or amoeboid envelope, in which state it then 

 appeared to me in the substance of the sponge (' Annals, '^ 

 1874, vol. xiv. pp. 329 and 350, pi. xx. fig. 3, a-c). 



Now, as the monociliated spongozoon of the ampullaceous 

 sac (a certain time after having been separated from its con- 



