402 Mr. H. J. Carter on the 



seed-like body of Spongilla, as it was called in my paper " On 

 the Identity in Structure and Composition of the so-called 

 Seed-like Body of Spongilla with the Winter-egg of the 

 Bryozoa" ('Annals,' 1859, vol. iii. p. 331, pi. viii.), as first 

 suggested by Meyen (Microscop. Journ. vol. i. p. 42, ap. 

 Johnston, footnote p. 154, B. S. 1842), and view it now again 

 as a simple ovum with modified form to meet the requirements 

 of the case — thus equal, as a whole and after this manner 

 only J to the " gastrula " of Hiickel — that is, our embryo of 

 Grantia compressa. 



Lastly, it becomes a matter for consideration what the nature 

 of the perfectly developed sponge is — if, in the end, the single 

 ovum comes out with a great number of ampuUaceous sacs, 

 composed of a still greater number of spongozoa. And this 

 brings us back to the point from which we started, viz. where 

 we found the earliest appearance of the ovum but a little larger 

 than a single spongozoon (PI. XX. figs. 2, a, & 3, a). Thence 

 the question whether this ovum was previously put forth 

 singly, as the product of a single spongozoon, or in plurality, 

 as the product of its ovary — and, finally, the question whether 

 the whole of the perfected sponge has not been evolved from 

 an ovule probably much smaller, in the first instance, than the 

 spongozoon itself. If so, then the spongozoon (PL XX. fig. 2, a), 

 must, ipso facto ^ be considered the expression of the Sponge, 

 in so far that it represents the stomach and the generative appa- 

 ratus aided by the rest of the body, which thus becomes analo- 

 gous to such accessories in the highest animals, although the 

 plurality of spongozoa scattered through the mass may more 

 nearly resemble in this respect the flower-buds of a plant. 

 Such, then, appears to be the nature of a sponge. 



Not only do the seed-like bodies of Spongilla vary in size 

 in the different species, but, as may be seen by my illustrations, 

 this is strikingly the case Avith the embryos respectively of 

 Halisarca lohnlaris^ Grantia compressa^ and Halichondria 

 simulans among the marine sponges, while the size of the 

 embryo itself also diff'ers greatly in the same individual. 

 Lastly, the constitution of the embryo, its colour, and ultimate 

 development also difi^er in different species ; so that here, as 

 well as everywhere else in connexion with the sponges, their 

 protean character is sustained by varieties and peculiarities 

 which must necessitate the examination of every species fi'om 

 the ovule to the parent before we can hope for a satisfactory 

 generalization. 



Having now premised the development of the sponge — 

 which, but for the pecuniary aid (fi'om the Government grant) 

 kindly given to me by the Royal Society, I should never have 



