314 ENTOMOLOGY FOR MEDICAL OFFICERS 



" nauplius " eye. Behind the antennae in the mid-ventral line 

 is the mouth, with all the other cephalothoracic appendages 

 crowded together on either side of it : these are the "mouth- 

 parts," and consist, in consecutive order, of a pair of mandibles, 

 two pairs of short, setose maxillse, and a pair of maxillipeds 

 or foot-jaws. 



The tail-like abdomen consists of 4 (female), or 5 (male) 

 segments, all of them destitute of appendages. Attached to 

 the first abdominal segment of the female is often seen a 

 pair of large oval egg-sacks, each of which may be about one- 

 third as long as the animal itself 



If a Cyclops be examined alive in a drop of water, 

 steadied by a cover-glass, the alimentary canal, which pulsates 

 vigorously, can be seen running from the mouth to the cleft 

 of the caudal fork. 



To study the development of Cyclops, a female carrying 

 egg-sacks should be taken up in a pipette and placed in a 

 small tube of water with a few pieces of duck-weed or a small 

 tuft of a Confervoid. The tube should then be corked for 

 safety, and left in the light. Within a few days, minute 

 whitish specks will be seen flitting through the water and 

 resting on the side of the tube. These are the "nauplius 

 larvae " of Cyclops. 



A nauplius examined under a low power of the micro- 

 scope discloses an oval body with three pairs of setose 

 appendages, of which the first is simple and the other two 

 are biramous. These are the future antennae and mandibles, 

 though in the present stage they are organs of locomotion. 

 At the fore end of the body, in the middle line, is a mass of 

 pigment — the " nauplius eye," which persists throughout life 

 as the sole organ of vision. Between the mandibles is the 

 mouth, and at the hinder end of the body is the anus. The 

 alimentary tube runs through the body in a straight line, 

 and within it may be seen the diatoms and spores of confervae 

 taken as food. 



In the course of a few days the nauplius is transformed 

 into the adult Cyclops by a succession of moults, in which 

 segments with their appendages, or buds of them, are added 

 at the posterior end of the body, but in front of the terminal 

 portion where the anus is situated. 



