GENUS: CRYPTOBIA 637 



consisting of a parabasal body and two blepliaroplasts. From each 

 blepharoplast arises an axoneme which passes through the cytoplasm as a 

 rhizoplast to the anterior end of the body. Here one enters a flagellum, 

 which is directed forwards, while the other passes backwards along the 

 border of an undulating membrane to become a flagellum at the posterior 

 end of the body. The question of the possible origin of trypanosomes 

 from these forms by the loss of the anteriorly directed flagellum has 

 been discussed above (p. 316). It seems very improbable that trypano- 

 somes have originated in this way. The primitive type from which they 

 have been evolved is presumably a flagellate of the leptomonas form seen 

 typically in insects, while the forms now being considered seem to have 

 sprung from Bodo or Cercomonas ancestors. In fact, the members of this 

 family are structurally very like species of Bodo and Cercomonas. From 

 the former they differ in the absence of the cytostome, and in the back- 

 wardly directed axoneme being attached to an undulating membrane, 

 while from the latter they differ in the possession of a kinetoplast. It is 

 probable that the forms which occur in the blood of fish have been derived 

 from intestinal forms which have invaded the blood-stream. 



In association with a blood habitat a method of transmission through 

 the agency of leeches has been evolved, while the purely intestinal forms 

 are presumably handed on directly from fish to fish by the ingestion of 

 forms which escape in the fgeces. The molluscan forms, which live in the 

 vesicula seminalis or spermatophores, are probably transmitted directly 

 from host to host during copulation. 



It will be most convenient to consider these flagellates under the 

 following headings— Invertebrate Forms, Intestinal Forms of Fish, and 

 Blood Forms of Fish. 



A. Invertebrate Forms. 



The first flagellate of this family to be seen was described by Leidy 

 (184:6) from the sexual organs of various species of snail {Helix) in America. 

 He named the flagellate Cryptobia helicis, but in the following year (1847) 

 renamed it Cryptoicus helicis, as the name Cryptohium had been previously 

 employed for a beetle. Diesing (1851) referred to it as Bodo helicis, while 

 Leidy (1851 and 1856) accepted Diesing's conclusion that it belonged to 

 Ehrenberg's genus Bodo. It was found by Keferstein and Ehlers (1860) 

 in Helix jwmatia in Germany, and was studied in detail by Friedrich (1909). 

 It was further studied by Jollos (1910), Crawley (1909), and by Delanoe 

 (quoted by Laveran and Mesnil, 1912) in France in H. pomatia, H. hor- 

 tensis, and H. nemoralis, and by Belaf (1916). It is evidently a common 

 parasite of the various species of Helix in America and Europe. The 

 correct name of this organism is clearly Cryptohia helicis Leidy, 1846, 



