622 FnsJi-Watcr Ibitomostraca. [October, 



served, often a delicate, transparent animal may be seen darting 

 about in the vessel like a fl.ish of li^ht, or if the lake be shal- 

 low and abounds in water plants the related form re{)resented 

 in Plate i may be seen. As it sprin<;s from side to side of the 

 jar it seems a living jewel, for the antenn.e and abdomen are 

 tipped with varying purple, and the body glows yellow and 

 scarlet, and if the bright-red egg-mass be present it is a con- 

 spicuous object. Place it under the microscope with a low power 

 and we can see the long flexible antennae, and if it is a male the 

 thickened basal joints can be seen terminating in a spine at the 

 thirteenth, where the geniculating joint is situated. rThe anten- 

 nules on either side of the head segment, which is distinct from the 

 tliorax in this species, and the stylets on the last joint of the 

 abdomen, with their seta-, are noted — when the antennules begin 

 to rotate like the paddles of a steamer, and bending the abdomen 

 and immediately launching a powerful *' kick " with the caudal 

 seta! spread out, at the same time that the antenme beat the 

 water like oars in the hands of an expert, the animal s[)rings out 

 of sight. Oite instinctively looks for the fellow some yards 

 away, but remembering that the whole animal is little over .06 

 of an inch long, we again adjust the slide and bring him into view. 



More abundant than the Diaptoniiis and better known, is the 

 Cyclops. Plate 11 represents a large species in which the hairs 

 are greatly elongated, especially on the caudal seta', the longest 

 pair of which resemble feather dusters. The Cyclops has received 

 more than its share of names, owing to the great difference 

 between different stages of its existence. If we place a female 

 Cyclops in a vial, in a few days little specks will be seen swim- 

 ming about in the water, and the eggs will have disappeared. 

 These specks prove to be the young of Cyclops, but so little like 

 the parent that it requires much faith to believe they will ever 

 assume its likeness. Instead of five pairs of feet there are but 

 three, and as we watch the growth of the animal, these prove to 

 be elementary antennae and jaws, while the true feet bud out of 

 segments not yet formed. Almost every i)ool furnishes another 

 example of the Cyclopoidca in the CantJiocaniptus which resembles 

 the Cyclops greatly, and goes through the same transformations. 

 The body tapers gradually with no marked distinction between 

 thorax and abdomen ; the egg-sac too is under the abdomen, and 

 has in connection with it a colorless tube. 



Perhaps the next animal to attract our attention will be a crca- 



