2 THE CANADIAN NATURALIST. [Vol. viii. 



ing the knowledge of the genus, that all new forms fall naturally 

 into one or other of these. To this rule the forms now under 

 consideration offer no exception, though representing both groups ; 

 /S. stagnalis and S. asperrima, belonging to the fluviatilis type, 

 S.flexispina and S. Ottawaensis, to that of lacustris. 

 In the first series, are included those spongillas in which the 

 gemmule, or reproductive capsule, is built up of birotulate spicula, 

 placed side by side, and arranged with their axes radially. In 

 the second, the capsules are more leathery, but covered, when 

 mature, with straight or curved spicula, arranged at right angles 

 to the radial lines. 



For details concerning the classification and morphology of the 

 Spongillidm, reference should be made to Dr. Bowerbank's and 

 Mr. Carter's Memoirs. 



I append first Dr. Bowerbank's description of S. Dawsoni, as 

 given in his monograph on the Spongillidct* 



Spongilla Dawsoni, Bowerbank. "Sponge sessile?, branch- 

 ing ; surface smooth, oscula and pores inconspicuous. Dermal 

 and interstitial membranes abundantly spiculous; spicula fusi- 

 formi-acerate, entirely spined ; spines numerous, short, and 

 conical. Skeleton-spicula acerate or subfusiformi-acerate. Ovaria 

 spherical : dermal spicula numerous, disposed in flat fasciculi, or 

 groups of spicula parallel to each other ; groups irregularly dis- 

 persed ; spicula acerate or subcylindrical, entirely spined ; spines 

 numerous, obtuse, and ill-defined. Sarcode aspiculous. Colour, 

 in the dried state, emerald-green. " 



Bab., River St. Lawrence, Montreal ; a lake near Brockville. 

 Dr. Bowerbank further adds, with reference ro this species: 

 " 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 disposed 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 propor- 

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

 regular acerate form, but occasionally become subfusiform." 



* Jfroc. Zool. ISoc. London, Nov. 1863, and Canadian Naturalist, 1864. 



