Some Sponges of the Ohio River. 185 



SOME SPONGES OF THE OHIO RIVER. 



By Geo. B. Twitchell. 



(Read December 6, 1887.) 



Perhaps the earliest mention of fresh water sponges is that of 

 Leonard Plukenet, in 1696. Linnaeus recognized two species: 

 Spongia lacustris and S. fliiviatilis^ the specific names of which are 

 still retained, although more scientific classification has put them 

 into different genera. These two species were founded on distinc- 

 tions of external form and habitat, both very variable features in 

 the sponges. Indeed, it is probable that the species lacustris pre- 

 fers rapidly running water, while the specimens found in the Ohio 

 River were in comparatively quiet water. Dr. J. H. Hunt has 

 frequently found them in the rapids of the Miami, and Mr. Ed- 

 ward Potts, of Philadelphia, says that the strongest and most vig- 

 orous specimens came from running waters. 



Since the time of Linnaeus much has been learned about these 

 organisms, better and more complete knowledge coming with the 

 improvements of the microscope. Such men as Bowerbank, Grant 

 and Carter have given the subject much thought and work. Europe, 

 Asia, Africa and the two Americas have contributed to the num- 

 ber of species. Quite a number of remarkable sponges have been 

 found in the Amazon River, while Fairmount Dam, on Schuylkill 

 River in Philadelphia, has been considered one of the richest local- 

 ities in the world for fresh-water sponges. 



The fresh-water sponges, unlike the sponges of commerce, 

 possess a skeleton whose fibre is entirely composed of siliceous 

 spicules, bound together by a very small amount of sarcode. So 

 that the least pressure will reduce a dry fresh-water sponge to 

 powder. The study of the vital parts is attended with so much 

 difficulty that it is only of late years that, with improved instru- 

 ments, a proi)er understanding of the subject has been attained. 

 But the spicules — upon which the classification is largely based — 

 are easily observed, and aside from their seientific value, make 

 beautiful objects for the microscope. 



The spicules of the skeletons of the different species are all 

 very similar, being simple needles of silica, sometimes slightly 

 curved, more or less pointed, with the shaft either smooth or cov- 



