272 AQUATIC MICROSCOPY FOR BEGINNERS. 



II. CanthocAmptus (Fig. 185). 



After Cyclops and Daphnia this is the commonest 

 fresh-water Entomostracan in the writer's vicinity. A 

 gathering of aquatic plants can seldom be made in this 

 neighborhood without obtaining many of the graceful 

 little Canthocdmpti. They are visible to the unaided 

 eye as small, flesh-colored, or pinkish lines darting 

 through the water in short jerks, after the manner of 

 most Entomostraca. Like all minute animals, they 

 will collect on the best-lighted side of the bottle, 

 where they may be easily captured with the dipping- 

 tube. 



The eye is single. The antennse are short and 

 somewhat hairy. The body is long, narrow, and sub- 

 cylindrical, being widest and thickest in front. There 

 is no distinct heart. The external ovary is single, and 

 is attached to the parent by the thinnest and appar- 

 ently most delicate filament although considerable 

 force is necessary to separate it from the body. The 

 eggs are round and opaque. The young differ greatly 

 from their mature aspect. Canthocamptus is found in 

 almost any shallow body of still water, and all the 

 year through, even occasionally in midwinter. It is 

 shown in side view in the figure, so as to exhibit the 

 single external ovary so characteristic of it. 



12. Cyclops (Fig. 186). 



This commonest of aJl fresh-water Entomostraca 

 has a single eye in the middle of the forehead, like the 

 giants of ancient story, a bifid tail adapted for swim- 

 ming, and two external ovaries, one on each side. 

 These ovaries are long, pear-shaped sacks filled with 

 dark, opaque eggs, and attached to the body by the 

 narrow or stem end of the pear. 



