306 THE CANADIAN NATURALIST. [Aug. 



from the same gentleman a further supply of fragments of this 

 species, containing ovaria, and giving a better idea of its form than 

 those first sent to me. The largest of the pieces sent was 1-| inch 

 in length and 2J- lines in diameter, evidently a portion of a longer 

 "branch. At the proximal end there is a short branch, 3 lines in 

 length and one line in diameter ; and the distal end divides into 

 two small branches of similar dimensions to the first, thus satis- 

 factorily indicating the branching habit of the species. In several 

 parts of this piece there are ovaries imbedded in the sponge, and 

 there were many others in the fragments of the same species that 

 accompanied it. The general external characters appear very like 

 those of the European species S. lacustris ; and from this simi- 

 larity, I have very little doubt of its surface in the living state 

 having been smooth and even, as in that species. In the Euro- 

 pean species the branches spring from a broad spreading base, 

 about half an inch in thickness ; and I think it highly probable 

 that the American species will be found to possess the same 

 habit. I could not detect oscula on any of the fragments in my 

 possession. 



The dermal and interstitial membranes abound with tension- 

 spicula, and especially the dermal one, in which they seem to 

 attain their fullest degree of development. Their normal form is 

 fusiformi-acerate ; but, from the abundant production of the 

 spines at their terminations, they frequently appear to be cylin- 

 drical rather than acerate. They are dispersed on these tissues 

 rather unevenly, abounding in some spots, while they are com- 

 paratively scarce in others. 



The spicula of the skeleton are of about the same proportions 

 as those of the European species. They are usually of the regular 

 acerate form, but occasionally become subfusiform. 



The spicula and their mode of arrangement in the dermis of 

 the ovarium cannot be readily seen without the aid of treatment 

 with hot nitric acid, in which they should be immersed for a few 

 seconds, and the acid should then be immediately diluted with 

 water, after which they should be dried on the glass, on which they 

 are to be mounted in Canada balsam. The spicula in the dermis 

 of adult ovaries are very abundant. They are similar in form 

 and proportions to those of the dermal membrane ; but, generally 

 speaking, they are more fully produced, and the greater portion 

 of them are subcylindrical from the profusion of spines at their 

 apices. Their form and mode of arrangement in the ovary render 



