442 THE CANADIAN NATURALIST. [Dec. 



arguments. It is now no longer a mere hypothetical supposition 

 — hitherto it was in reality no more — but a real scientific explana- 

 tion, borne out by well established facts and undeniable analo- 

 gies from living forms.* To Dr. Gray we certainly owe the first 

 intimation of this analogy between Leskia and Cystidea, but 

 while the knowledge of that genus rested on a single examination, 

 there might still linger some doubt whether its importance in this 

 respect had not possibly been overrated. Science, therefore, must 

 be highly indebted to Prof. Loven for his small but valuable 

 memoir, and for the excellent observations laid down in it. The 

 absolute denying of the existence of an apical orifice in that place 

 where, in other Cystidea at least, such an orifice was also believed 

 to exist, is particularly recommended to the attention of future 

 investigators of Cystidea, as bearing upon the very heart of the 

 question. Adhuc sub jadice lissit ! 



NOTE BY E. BILLINGS, F.G.S. 



Professor Liitken is certainly mistaken when he makes use of 

 the expression, " It is now no longer a mere hypothetical supposition, 

 hitherto it was in reality no more," etc. The earlier Palaeonto- 

 logists, Gyllenhal, Wahlenberg, Pander and Hisinger, described 

 the valvular orifice of the Cystidea as the mouth, but they never 

 proved it to be so. Indeed they could not do so, for the data, i. e., 

 the structure and functions of the arms of the Crinoids living in 

 the sea at the present time, were not known. In 1845 Leopold 

 von Buch pronounced the aperture in question to be an ovarian 

 orifice, and the small one in the apex the mouth. His views 

 were adopted by Prof. E. Forbes, in his beautiful memoir on the 

 British Cystidea and by Prof. J. Hall in the Palaeontology of 

 New York. In my first attempt at describing fossils, in 1854, I 

 followed these three last named distinguished Naturalists, in a 

 paper on the Cystidea of the Trenton Limestone at Ottawa, 

 published in the Canadian Journal. But in 1858, while re- 

 investigating the subject for my Decade, (No. 3,) I saw that they 

 were wrong, and proved it according to the ordinary rules of com- 

 parative anatomy. If any organ of an extinct animal is the exact 

 homologue of an organ possessed by an existing species (of the 

 the same zoological group), its function must have been the same. 



* To these analogies might be added, that between the valves of 

 Cystidese and those of the young (larval) Antedon. 



