34 The Miceoscope. 



To properly investigate these aquatic creatures, the microscopist 

 should be able to successfully use the microtome. The worms are,, 

 as a rule, transparent, but the attempt to study the various part& 

 and organs through the tegumentary coat of the living, writhing 

 animal is somewhat difficult, and apt to be followed by errors of 

 interpretation. The histology of the various parts can be satisfac- 

 torily investigated only by means of stained and serial sections, but 

 microtome work over creatures whose bodies are visible to the naked 

 eye chiefly by reason of their length and not on account of their size 

 in other directions, is work for the expert. And here is an obstacle. 

 It is not every microscopical student, working alone, who can possess 

 the instrument needed for such delicate cutting, and he has con- 

 sequently not acquired the skill necessary, not only for the manipu- 

 lation of the microtome, but for the preliminary treatment of the 

 specimens. This is the writer's unfortunate situation, although he 

 has been so highly favored as to obtain the assistance of an expert 

 microtomist, who will take one of the subjects of this paper, and pre- 

 pare it for future study, the results of which will be embodied in 

 another essay supplementary to the present one. The following 

 description, therefore, of some points in the anatomy of two pre- 

 sumably undescribed aquatic worms is superficial, but it is the result 

 of prolonged and repeated study of the living creatures. 



II. 



jEolosoma distichum, sp. NOV. (fig. 1.) 

 For three years past the writer has been finding the worms here 

 referred to, often in great p rofusion. They appear to favor the depth 

 of stale or even partially decayed collections of aquatic plants left 

 standing in the light and warmth of a room, occasionally presenting 

 themselves in abundance in such places. I have no recollection of 

 capturing any from an open pond or pool. They were first obtained 

 among a decaying mass of Sphagnum, which had been gathered 

 several months before and had remained in a covered vessel until the 

 water was thickly coated with a slimy mass of microscopic fu^ngi, on 

 the surface of which the worms glided in great numbers, and where 

 they seemed to find a plentiful supply of food. More recently they 

 have developed in such quantities in an old infusion of dead autumn 

 leaves that the small and almost filiform bodies became conspicuous 

 by reason of their numbers. In a vessel containing decaying 

 Lemna, Myriophylhnn and other aquatic plants they have appeared 

 suddenly and plentifully. In a similar mass of decaying vegetation 

 originally brought from the cypress swamps of Southern Florida, 



