90 Mr. W. Marshall on the 



XI. — Remarks on the Goelenterate Nature of the Sponges. 

 By William Marshall*. 



On different occasions I have given expression to mv con- 

 viction that the Sponges are Coelenterata — a conviction 

 which I share with Leuckart, Hackel, Von Lendenfeld, and 

 others. It originates from a series of morphological and 

 ontogenetic facts, of which radial symmetry is not the least 

 important. I have formulated my opinion about as follows : 

 — that the Sponges are Coelenterata, in which, in consequence 

 of the (phylogenetically speaking) very early occurrence of 

 sessility, profound retrogressions had taken place, induced 

 especially by a colossal overgrowth of the mesoderm. 



Quite recently treatises have appeared from two sources on 

 the systematic position of the Sponges. One of them (which 

 certainly completely ignores my conception and its results) 

 argues against the Sponges belonging to the Coelenterata, and 

 indeed to the Metazoa at all ; while the other arrives at the 

 result that, if the Sponges and C<:)elenterata did possess com- 

 mon ancestors, the former must have branched off from the 

 latter at a time when true typical Coelenterate characters had 

 not yet been acquired. As both treatises have distinguished 

 spongiologists for their authors they call for the greatest con- 

 sideration ; and this the more, because they diverge so widely 

 from each other in the result of their deductions. One of these 

 memoirs is the work of F. E. Schulze f, the other of W. J. 

 Sollas|; and although the former appeared somewhat later 

 than the second, we shall here discuss it first, as its treatment 

 of the subject is more general. 



Schulze subjects the two opposite opinions — according to 

 one of which the Sponges are colonies of Protozoa (Choano- 

 flagellata), and according to the other Coelenterata — to a 

 thorough criticism. 



Following the lead of James Clark and Carter, Savile 

 Kent especially, with whom Biitschli has also recently asso- 

 ciated himself, had taken it upon himself, on the foundation of 

 observations partly correct, but partly also quite erroneous, 

 to demonstrate the Protozoan nature of the Sponges, in which 

 he laid particular stress upon the nature of the flagellate cells 

 and the processes of development. The flagellate cells, when 



* Translated from an advance copy, communicated by Dr. G. J. Hinde, 

 F.G.S., of the paper in the ' Jenaische Zeitschrift,' Baud xviii. pp. 868- 

 880. 



t Sitzungsb. Berl. Akad. d. Wiss. 1885, pp. 179-191 ; translated in 

 Ann. & Mag. Nat. Hist. ser. o, vol. xv. pp. 3G5-377 (May 188-5). 



\ Quart. Joaru. Microsc. Sci. u. ser. vol. xxiv, pp. 603-021. 



