Section IV, 1889 [ 85 J Trans. Roy. Soc. Canada. 



YIl. — Fresh-ivater Sponges of Canada and Neirfoundlarid. (Plate IV. j 



By A. H. MacKay, rriiuipal of Halifax Academy, N. S. 



(Read May 20, 1889.) 



lu this synopsis, nothing- beyond the merest outline is intended, just sufficient to 

 indicate the extent to which the Spongillidaî of Canada have been observed, and to facili- 

 tate further investigation. 



Twenty-six years ago, Bowerbank described (Proc. Zool. Soc. London, Nov. 1863) a 

 sponge, collected by the presejit Sir J. "W. Dawson in the St. Lawrence, under the name 

 SpoHgilla Dawsoni. In the same year, he also described another species from a lake in the 

 Cascade Mountains, under the name Spongilla Lonlii. Twelve years later, Dr. G. M. 

 Dawson described (Canadian Naturalist and Greologist, Sept., 18*75) several species from 

 the Lake of the "Woods, the Ottawa and the St. Lawrence, which made in all six Canadian 

 species. These are now redixced to three, the others being classed as varieties. In 

 188*7 Prof. Ramsay "Wright published " The Systematic Position of the Spongidœ." 

 Since 1883, the author has been observing the fresh-water sponges in their habitats in 

 Nova Scotia and eastern Newfoundland, and has examined a few small collections from 

 the central and western provinces of the Dominion. The warmest acknowledgments of 

 inspiration and scientific aid received are due from the author to Messrs. Henry J. 

 Carter, of England, and Edward Potts, of Philadelphia. Much of our common work has 

 been published from time to time by the former in ' The Annals and Magazine of Natural 

 History,' London ; and by the latter in the ' Proceedings of the Academy.' 



G-ENERAii Appearance and Habitat. — The Spongillidae grow in still or flowing 

 fresh water, usually as greenish masses attached to some basis of support such as sub- 

 merged timber, branches, stones, firm gravel, or grass culms. They may appear as minute 

 specks, colorless when beneath cover from the light ; or as thin encrustations ; or more 

 massive, over an inch in thickness and some feet in extent ; or bearing lobular processes ; 

 or branching erect ; or in flaccid filaments. At a distance, their position and form dis- 

 tinguish them from biinches of green Algœ. Close at hand, they are seen to be masses of 

 a slimy kind of flesh investing a friable meshwork structure built up out of siliceous 

 needles averaging the one-hundredth part of an inch. Their animal character is sug- 

 gested by a peculiar though not unpleasant odor when fresh, and especially by a fetid 

 putrescence if not rapidly dried or put into some preservative fluid. Turbidity of water 

 is unfavorable to their development. The greatest luxuriance is observable where such 

 a condition seldom exists. The injurious effect is probably due to the fouling of their 

 system of water circulation. The quantity of pure water, if sufficient, appears to make 

 but little difference. They are found not only in our great lakes and rivers, but in mill- 



