REPORT ON THE CALCAREA. 03 



296-327), and, agreeing with him thoroughly upon the matter, I see no reason to repeat 

 here what has already been quite sufficiently discussed. I refer the reader to the passages 

 in question in the Monograph, and can only express my astonishment that Hseckel havinc 

 made out the existence of the correlations above mentioned in such a brilliant manner, 

 did not give them any application in his system. 



It was, however, the right way, and if the following out of these principles amount 

 to nothing with reference to the Asconidae, it only proves, either that the Ascones are not 

 to be divided into many genera at all, or that our knowledge of this group is insufficient. 

 I think both suppositions have some truth in them. At all events, there is at present no 

 possibility of giving a detailed system of this Order. The exterior shape is in this group — 

 perhaps with exception of the forms provided with solid peduncle — really without any 

 significance, at least it is quite unfit for the establishment of genera. The Wagnerella of 

 Mereschkowsky, 1 proved to be a Protozoon 2 , and, except the still doubtful Mcebiusspongia 

 parasitica, Duncan, 3 there are in the Family only two groups which admit of a generic 

 distinction, the distinction consisting in the differences of the embryonic development, 

 characterised in some cases by Parenchyruula, in others by Amphiblastula. Unfortunately 

 the embryology of most of the Asconidae is still surrounded by the mist of uncertainty, 

 and it is only to five species (Ascetta primordialis, Ascetta blanca, Ascetta clathrus, 

 Ascandralieberkuhnii, and Ascandra contorta,) that the foregoing remark can be applied. 

 Therefore, till zoology shall have been enriched by more extended investigations upon this 

 matter, I propose to unite provisionally all the Asconidae under the same generic name, 

 and, following the law of priority, I propose the name — 



Leucosolenia, Bowerbank 4 . 



The necessity for such a temporary measure is by no means satisfactory, but still it is 

 always better to confess frankly that our knowledge is imperfect, and that there remains 

 much still to be done, than to allow ourselves to be led astray by the assurance, however 

 flattering, that everything is already completed and the question exhausted. 



We have every reason to consider ourselves much more advanced with respect to the 

 Heteroccela. There are to be found characters of undoubted generic significance, i.e., char- 

 acters of sufficient constancy, and allowing numerous modifications, either in the direction 

 of a further development, or in the direction of different variations. The nature of the 

 spicules proclaimed by Prof. Hseckel as furnishing good generic characters, satisfies only 

 the second condition, and therefore they are unfit for generic distinctions, apart from the 

 consideration that in a group of such a low organisation as Calcarea a generic character 



1 Ann. and Mag. Nat. Hist., pit. 5, vol. i. p. 70, 1878. 8 Paul Mayer, Zool. Anz., No. 32, \\ 357, 1879. 



3 Juurn. Boy. Micr. Soc, vol. iii. p. 377, 1880. ' Phil. Trans., Loiulon, vol. clii. p. 1093, 1SG2. 



