184 AQUATIC MICROSCOPY FOR BEGINNERS. 



is small, as the length of the body is only about -j^ 

 inch. When swimming its movements are more rapid 

 than those of Chsetonotus. 



The mouth is nearly apical. The oesophagus has a 

 snapping movement similar to that visible in Chaeto- 

 notus, although the food is usually engulfed by suction, 

 living and comparatively large Infusoria being taken 

 as well as organic particles. 



Dasydytes saltitans does not seem to be common. It 

 was originally discovered near Trenton, N. J., where 

 it is not rare, and it has been found near West Point, 

 N. Y. It has not been reported elsewhere. 



2. ICTHYDIUM. 



1. This resembles a Chsetonotus with a smooth, naked 



back, all scales, spines and prickles being absent.. 

 The spines and other dorsal appendages are rep- 

 resented by two hairs standing almost vertically 

 on the neck, and two on the rear part of the back. 

 These are usually seen with difficulty, but they are 

 present on all the species, even the scaly and the 

 spinous ones of Chsetonotus: The ^gg of this 

 species is also smooth. In other particulars it re- 

 sembles Chsetonotus. This is Icthydium podura'. 



2. The characteristic of this form is in the deep trans- 



verse furrows conspicuously developed on the back 

 and sides. The body is transparent, and un- 

 usually soft and flexible. The posterior region be- 

 tween the arch of the back and the caudal furca- 

 tion is narrowed, and much longer .than in other 

 species. The oesophagus is short, being not more 

 than one-sixth the length of the body. Icthydium 

 sulcatus. 



