NEMATODA 223 



accomplished Russian traveller, who lost his life in a snow- 

 storm on the Alps), science stands indebted for this memorable 

 advance. Fedschenko showed that the embryos of Dracunculi, 

 after quitting the human host, succeed in effecting an entry 

 into the bodies of entomostracous crustaceans belonging to the 

 genus Cyclops. Within these intermediary bearers, after 

 twelve hours' sojourn, the embryos undergo a change of skin, 

 attended with subsequent growth. Here they remain to com- 

 plete their larval development, which takes place within a 

 period of five weeks, or, as Fedschenko himself told me, one 

 month and six days. At length, as perfected larvse, they are, 

 together with their crustacean hosts, transmitted to the stomach 

 of the ultimate or human bearer. It is probable that sexual 

 maturity is next acquired within the human stomach, copula- 

 tion following. After this, the females migrate to the situa- 

 tions in which they are found beneath the skin of the human 

 bearer, whilst the males perish and pass out with the faeces. 

 Thus much I gathered from M. Fedschenko himself when he 

 visited this country, and I possess a sketch of the larvae made 

 by him at the time (October 23rd, 1873). One of the figures 

 represents a larva which has undergone ecdysis, the long and 

 narrow embryonic tail being supplanted by one which is blunt 

 and forked at the tip. The somatic contents of the embryo 

 have at the same time differentiated into a complete intestinal 

 tube, and a constriction marks the junction of the oesophagus 

 with the stomach. There is also internally an oval- shaped 

 mass of cells near the centre of the body. These represent 

 the commencement of the reproductive organs. 



What I had gathered from Fedschenko in conversation thus 

 epitomises that which has since been much more fully stated 

 by Leuckart ; and it is only fair to add that the Eussian 

 traveller was led up to his discovery by the previous investi- 

 gations of Leuckart respecting the young of Cucullanus. The 

 Leipsic helminth olo gist had, indeed, specially instructed Fed- 

 schenko as to the probable source of Dracunculus. 



It is often thus that science makes its clear advances, since 

 a master-mind is needed to set others on the right track. The 

 embryos of Cucullanus and Dracunculus bear a close resem- 

 blance to each other, and the similarity of the types is 

 continued on, though not in the same degree, in the next stage 

 of larval growth, after ecdysis. The higher larvse of both have 

 their tails trifurcate at the tip, the head of the Dracunculus- 



