36 PROFESSOU ALIMAN. 



it with its tentacles and other parts extended, and at the 

 same time hardened by the reagent so as to allow of sections 

 being made for microscopical examination. In some cases 

 he subjects these sections to subsequent maceration in Miiller's 

 solution, and the iodine and serum solution, and then ex- 

 amines them for minute structure under Gundlach's or 

 Hartnack's No. 9 immersion lens. 



He has thus succeeded in making out with great detail 

 the minute structure of Cordylophora, and I propose to give 

 here some account of the more important results of his 

 examination. 



After confirming the cellular nature of the ectoderm and 

 the endoderm, and the existence in certain parts of the animal 

 of a fibrillated muscular layer between the two, as described 

 in my original paper on Cordijlopliora lacustris, he main- 

 tains the important additional fact of the existence of a 

 structureless hyaline membrane, which also lies between 

 ectoderm and endoderm, and in those parts where the mus- 

 cular layer exists, at the inner or endodermic side of this 

 layer. 



This hyaline membrane is the supporting lamina, " stiitz- 

 lamelle" of Reichert, who recognises its presence in the same 

 position in other hydroids, though he asserts that I con- 

 founded it with my muscular layer whose existence he alto- 

 gether denies, while he maintains that there is no true cellular 

 structure in the ectoderm. 



I am willing to accept Reichert's demonstration of this 

 hyaline " stiitzlamelle" confirmed as it is by the more recent 

 researches of Schulze. Indeed, I have been long aware of 

 the appearance of a narrow clear space between the ecto- 

 derm and endoderm as visible in sections of many hydroids, 

 and have in many cases represented it in my published 

 figures, though I could never convince myself that the ap- 

 pearance here of a narrow hyaline space ought to be regarded 

 as the expression of an independent membrane. Schulze's 

 mode of investigation, however, appears to me now to set 

 this question pretty much at rest, and to justify us in regard- 

 ing the "stiitzlamelle" as a second element lying between 

 ectoderm and endoderm, the muscular layer being the other. 



The formation of the endoderm of the hydranths and 

 coenosare out of a single layer of large elongated cells very 

 similar to those described and figured by myself, is also 

 maintained by Schulze, but he can in no case find the secon- 

 dary cells which I have described as existing in the largo 

 endodermal cells, and to which I believed myself justified 

 in assigning a secreting function. 



