136 Tin-: nautilus. 



while quite near, in deeper and running water, the mussels were 

 alive and healthy as usual. There is hardly a doubt as to the 

 cause of death in this instance: fish certainly did not kill them, 

 nor any other animal; but evidently it was the sun heating the 

 bottom and the water, probably also changing the latter, and in 

 addition, pi'omoting the development of bacteria, etc., causing 

 disease. 



As to the wholesale destruction related by Dr. Strode, the case is 

 somewhat different, since there was a lake 5 miles long, but very 

 shallow, as the doctor says in the April number, and Anod. corpu- 

 lenta lived near the shore. May we not draw the conclusion from 

 these facts, that the long continued heat and evaporation, directly 

 and indirectly, probably were the cause of that terrible dying? On 

 the other hand, we may think that one species is more delicate, more 

 predisposed to and less resistant against certain destructive agents. 

 It is too well known that the past late summer and fall were 

 exceptionally dry, and I presume that not only millions of fish as 

 well as Najades and other fresh-water animals fell its victims in a 

 great part of the country — from drying up as well as from deteriora- 

 tion of the water — but also of the minute and delicate land snails a 

 great percentage probably perished. 



In October past I visited a few small ponds, sloughs, where the 

 water had dried up for the most part in some, still standing 1-1 2 

 feet deep in others. ^[ost of the aquatic plants, thrifty in spring 

 and early summer, were rotten or in poor condition, a dark, sooty 

 mass covering the bottom, evidently the remnants of decayed organic 

 matter. Of mollusca, there were very few alive, and to my surprise, 

 the Limncnidcd were almost all dead, while in one place numerous 

 Amnicola were living, in another Valvata-trlcarinala: is it not 

 strange that " pulmonata" could not survive where branchiata wei-e 

 doing well ? 



Again in November I found on Tuscarawas river, a small mud 

 hole, about 5 feet long, the water two feet deep, on the bottom a 

 thick layer of that dark, soot-like mass. There were a number of 

 Melantho, evidently in good health, while I could not detect a single 

 specimen of Livmcea, Planorbis, Physa or Ancylus. 



These observations were made somewhat hastily, and might have 

 been more exact; yet I think they are not without some interest. 



