some American Freshwater Sponges. 21 



Academy, Pictou, N. S., from whom the speaker had recently 

 received a collection of sponges, phenomenal in its character, 

 both as regards the number of genera and species represented 

 and the excellent judgment that had attached to most of them 

 their proper names from apparently very insufficient data. 

 The collection was the result of a few clays' search within a 

 limited district, " from lakes in and near the watershed of 

 Nova Scotia, near the borders of the three counties of Pictou, 

 Guysboro, and Antigonish," at elevations of from 100 to 700 

 feet above sea-level. Of the genus Spongilla it contains three 

 species, S. lacustris } S. fragilis, and 8. iglooiformis • of the 

 genus Meyenia two species, M. Jluviatilis and M. Everetti] 

 of the genus Heteromegenia two, H. argyrosperma and H. 

 Byderi- and of the genus Tubella one species, T. pennsyl- 

 vanica — eight species, representing four genera. Besides these 

 there were small specimens of another species, evidently new, 

 but whose generic relations could not be determined on account 

 of the absence of statoblasts. 



In some respects the most important find in the collection is 

 Meyenia Everetti, Mills, this being only the second instance in 

 which the species has been discovered. The original locality 

 was Gilder Pond, upon Mt. Everett, in Berkshire Co., Mass., 

 at an elevation of 1800 or 2000 feet above the sea. It was 

 there collected by Dr. F. Wolle and Mr, H. S. Kitchel, of 

 Bethlehem, Pa., well known for their invaluable work among 

 the desmids and diatoms, and examined simultaneously by 

 Mr. H. Mills, of Buffalo, N. Y,, and the speaker. Its most 

 striking peculiarity is the presence all through the dermal 

 tissues of very minute birotulate spicules, the only instance in 

 which these have been observed as characteristic features of 

 the dermal surface in any freshwater sponges, unless the com- 

 plicated forms found in Meyenia piumosa } Carter , may be con- 

 sidered an exception. 



These birotulates in the present collection average one third 

 longer than those before examined and are in every way more 

 robust. The speaker was gratified in finding this confirma- 

 tion of a rule which he has long since observed to hold 

 amongst the infinite variations of size and form noticeable in 

 collections of the same species from various localities, viz. that 

 the spicules of all species increase regularly in size and 

 solidity as we descend from high altitudes towards the sea- 

 level, where is found the extreme limit of the series. He does 

 not attribute this gradation to a change of climatic conditions, 

 but more probably to a gradual and constant improvement in 

 the food-supply or in the siliceous constituent of the water. 

 He has traced the workings of the rule more particularly 



