707 



four to forty-eight hours after the Cyclops were placed in contact with 

 the embryos all had left the mid-gut and were found lying in the body 

 cavity ; no trace of digested embryos was seen in the alimentary tract. 

 Roubaud states that the naupilus larva of Cyclops is just as susceptible 

 to infection as the adult crustacean, and that it is not uncommon to find 

 three or four embryos in a single Cyclops larva. 



Roubaud has studied the development of the embryo in Cyclops in 

 Dahomey, and has confirmed the observations of Leiper. The embryo 

 may remain unchanged for ten days after entering the invertebrate host, 

 but as a rule the first sheath forms about the eighth day (larval stage), and 

 by the fourteenth day it enters on its second stage. The pointed tail of 

 the young embryo is replaced by a short blunt process, and though the 

 striation on the integument is still visible, it is much less apparent. The 

 larva is cylindrical in shape and measures 0*5 mm. in length, and is 

 much less motile than in the first stage. Forty-two days later it has 

 increased in size and now measures 0*6 mm.; its mouth develops into two 

 distinct lips, and the posterior third of the body becomes of a yellowish 

 brown colour. At this stage the larva is entirely quiescent and lies 

 coiled up in the body cavity of its host. Roubaud states that no 

 papillae could be made out at the end of its body, and that the tail is 

 conical and not trilobed. Although he carried out several transmission 

 experiments by feeding monkeys with infected Cyclops he was unable 

 to infect them with Guinea-worm. Roubaud believes that endemic 

 dracontiasis depends on a complex equilibrium between, (1) the time 

 required for the annual development of the adult female D. medinensis 

 in man, (2) the regular recurrence of the necessary seasonal conditions, 

 and (3) the conditions of human existence which favour transmission 

 by Cyclops. 



The body of Cyclops is pear-shaped, the broad end being anterior and 

 the dorsal surface convex (Plate LXXXIX, figs. 4 and 5) ; the posterior 



end is attenuated and ends in two blunt processes 



Anatomy of Cyclops 



armed with feathery stylets. The cephalothorax is (Plate LXXXIX, 

 completely covered by a convex plate of chitin, the figs. 4 and 5) 



carapace, which is produced around the sides to- The cephalothorax 



. . and its appendages 



wards the ventral surface. Arising from each antero- 



lateral border on the ventral surface is a long attenuated process known 

 as the antennule ; this consists of fourteen segments, of which the basal 

 and apical are the longest, the intermediate segments being very short ; 

 the apical segment is armed with a number of branched spines. The 

 antennules can be raised away from the body or pressed close into 



