708 MEDICAL ENTOMOLOGY 



the ventral surface ; they are the principal organs of locomotion, the 

 animal propelling itself in short jerks by rapidly flexing them. The 

 antennae are inserted just internal to the insertion of the antennules and 

 are uniramous ; each antenna consists of three segments, the basal one 

 being the shortest, the apical segment armed with a few long spines. 

 Between the insertions of the antennae is a short spinous process, the 

 rostrum, and directly above this on the dorsal surface is a large pigment- 

 ed spot, the median eye. 



Further back on the ventral surface and in the median line is the 

 mouth opening, on each side of which are the mandibles and maxillae ; 



the mandible consists of a short bar of chitin with the 

 The mouth parts . , . . , . , . , , . , 



inner end produced into a point, and is furnished with 



numerous short stiff spines. The maxillae are a little further back and 

 are much more conspicuous ; each maxilla consists of two segments, of 

 which the external one, or exopodite, is the larger, and is shaped like a 

 claw, its tip being bidentate ; the endopodite is much smaller, extending 

 up to about half the length of the exopodite ; it is armed with stiff 

 spines. 



The first pair of legs arise from the sides of the first thoracic segment, 

 which in this copepod has become fused with the head. The second 



pair appear to arise from the first thoracic segment, 

 Thoracic and abdomi- r , r ,. , r? u i 



nal segments and m reallt y from the second segment. Each leg is 



their appendages biramose and consists of a large basal segment, the 

 first protopodite, and a shorter apical segment, the 

 second protopodite, to which are attached the endopodite and exopodite, 

 each consisting of three segments, the apical one of which is armed with 

 long stout spines. The second, third, and fourth legs arise from the 

 corresponding thoracic segments ; the fifth, like the preceding ones, is 

 free and is armed with a pair of vestigial limbs. The sixth segment 

 bears the genital aperture, and in the female is united to the first 

 abdominal segment ; the egg sacs are attached at its sides. The fourth 

 abdominal segment is bifid, and ends in two blunt processes armed with 

 long feathery spines ; the anal opening is situated on the dorsal surface 

 in the middle line. The abdominal segments are without any appendages. 



The alimentary tract is simple, extending directly from the mouth 

 to the anus, with a dilated portion, referred to as the stomach, in the 

 middle. It is in the stomach that the embryos of Dracnnculus medi- 

 nensis are found. 



The life history of Cyclops is easily followed under artificial conditions. 

 An egg-bearing female is selected, and placed in a vessel of water which 



