ENTOZOA 433 



A certain amount of order has been introduced into this mass of material by the 

 establishment of certain sub-groups, and by the giving of a new generic name to the 

 members of these subdivisions ; thus in 1891 Blanchard and Railliet' established the 

 genus Davainea ; in 1892 Railliet" suggested tvi^o new generic names, Drepanidotaenia 

 and Dicranotaejiia, for certain tapeworms inhabiting, for the most part, domestic birds. 

 These are characterised chiefly by the nature of the hooks. In the following year 

 Diamare^ founded the genus Cotiignia, in which the generative organs are double and 

 have two pores, but which is distinct from the genus Dipylidium of Leuckart. All 

 these genera are characteristic avian tapeworms, and are, with but very few excep- 

 tions, confined to birds. 



There is little doubt that the tapeworm which I have described above from the 

 intestine of Hemignatluis procerus corresponds with a Drepanidotaenia of Railliet\ who 

 defines his genus as follows : 



" Tapeworms provided with a simple crown of uniform hooks, which are usually 

 few in number ; the outer limb (manche) of the forked base of the hooks is much longer 

 than the inner (garde), which is always slight ; the point is directed backwards when 

 the rostrum is withdrawn. The majority live in the intestines of aquatic birds. Their 

 larva is a Cysticercoid, and is found encysted in the bodies of small fresh-water 

 Crustacea." - 



Railliet describes eight species of Drepanidotaenia ; in one of these the genital 

 pores are on alternate sides of the body in successive segments ; the remaining seven 

 species are unilateral in this respect, but they fall into two groups, — one, with three 

 species, in which the number of hooks is eight ; and the other, with four species, in 

 which the number of hooks is ten. 



It is to this latter group that we must add the tapeworm from H. procerus. The 

 four species D. anatina, D. sinuosa, D. setigera, and D. tenuirostris differ inter se in 

 several respects, but perhaps the simplest way of determining the species is by measuring 

 their hooks. Of these four species, D. hemigtiathi most nearly resembles D. tenui- 

 rostris, which occurs in certain of the ducks ; it differs, however, markedly in size, being 

 when mature about ^ to jlj the length of the last named. It resembles D. tenuirostris 

 in the length of its hooks in the head, which in the latter are 20 — 22,[i., in the former 

 are 18 to 23 ^u, ; but whereas the hooks of the embryo are about the same length in the 

 new species, i.e. about 20 /x, in D. temiirostris they are but 7 /a. The neck is short, not 

 long as in the last-named species, and the eggs are small, about 40 — 50 /a in diameter, 

 and spherical in shape, not cylindrical as Krabbe' figures them, with a length of 85^01. 

 The hooks also differ in shape ; those of D. tenuirostris have a much more strongly 



' Mem. Soc. Zool. France, tome iv. 1891, p. 420. 



^ Ibid, tome xvii. 1892, p. 115. 



' Boll. Soc. Napoli, ser. i, vol. vii. 1893, p. 9. 



' Traite de Zoologie medicale et agricole, Paris, 1895, p. 298. 



' Danske Selsk. Skr. viii. 1870, p. 249. 



56 — 2 



