490 Dr. Bowerbank on certain Species oj Sjjonges. 



S. pulchella, represented in plate Ixxiv. fig. 10, ' Philosophical 

 Transactions of the Royal Society ' for 1862, with the corre- 

 sponding representation of the skeleton-structure of 8. Ilolds- 

 worthii (Proc. Zool. Soc. 1873, pi. vi. fig. 7). There is a slight 

 difference in the size of the fibres in the two species, but not 

 in the mode of their arrangement. 



If it will be any satisfaction to Dr. Gray, I Avill explain to 

 liim my reasons for designating the Ceylon sponge Spongio- 

 nella Iloldsioorthii. Esper, and most of the old writers on 

 natural history, had but one genus for the whole of the 

 Spongiadge — that of Spongia ; and their determinations of 

 species were based on external characters only. The conse- 

 quence has been such an inextricable confusion, that a 

 satisfactory determination or recognition of their species can 

 scarcely ever be arrived at. 



In the first place, the Ceylon sponge is not a Spongia, but 

 a Spongionella. Esper's Spongia papyracea tab. Ixv. and 

 Spongia papyracea tab. Ixv. A have every appearance of being 

 separate species, as far as we can judge by the form and texture 

 represented ; and independent of the variations in form, sub- 

 stance, and external characters in these two, there are several 

 Britisli species, and a very considerable number of African 

 and Australian ones, in my possession that, regarding only 

 form and substance, would quite as readily serve as the types 

 of Esper's figures as those brought home by Mr. Holds worth. 

 Esper's figures exhibit no structural characters by which a 

 species can be satisfactorily determined. I thought therefore 

 that it was most for the interests of science that Mr. Holds- 

 worth's sponge should stand upon its own merits, and that 

 not only the best type of its average external form, but also 

 its anatomical structure should be accurately represented and 

 described, so as to avoid future misconceptions on the 

 subject. 



An equal degree of careless error pervades his criticism of 

 the sponge I have described in the same report on Mr. Holds- 

 worth's Ceylon sponges as Isodictya Donnani. No one who 

 really knows the structure of the genus Isodictya can fail to 

 recognize it in figure 3, pi. vi. Proc. Zool. Soc. Nor can 

 tlie veriest tyro in sponge-anatomy for a moment imagine it to 

 be a Dictyocylindrus. I really cannot imagine that Mr. Carter 

 has justified such wild statements on that subject as Dr. Gray 

 has attributed to him. 



Dr. Gray has for the third time, in the 'Annals and Maga- 

 zine of Natural History ' for September last, ventilated his 

 remarkably visionary scheme of arranging the Spongiadas by 

 the forms of their spicula. As I have criticised his very im- 



