IIELMINTHOLOGY HELMINTHES NEMATODES. 449 



HELMINTHES NEMATODES. 



Dujardin (Annales d. Sc. Nat. torn, xx, 1843, p. 332, pi. 

 14) has observed in various Mammalia, in the Shrew-mouse, 

 Field-mouse, Falcon, Sparrow-hawk, Lark, Jackdaw, 

 Magpie, Jay, Common Fowl, Salamander, Carp, and Rudd 

 (Plotzeu), species of Trichosoma, and for the most part in 

 the small intestine of the animals above named ; but in the 

 Shrew-mouse he met with Trichosomata also in the spleen, 

 Avhich, as he supposed, might have reached that organ in 

 the course of their migrations. He has also particularly 

 described the digestive and generative organs of this worm, 

 and distinguishes two modifications of the male sexual 

 organs. Thus several Trichosomata, among others T. con- 

 tortum and inflexion, have a thick penis, with a short smooth 

 sheath, whilst others, e. g. Tr. splenaeum, Duj., from the 

 Shrew-mouse and Lark are furnished with a very slender and 

 flexible penis, the long sheath (prseputium) of which has a 

 rough aspect from the transverse wrinkles on its surface. 

 The females belonging to this latter Trichosoma present at 

 the vulva a remarkable appendage in the form of a short 

 cylinder directed backwards. A simple uterus and ova are 

 always present. The ova, whilst passing in a single series 

 one behind the other through the lower end of the uterine 

 pouch, acquire a special shell ; the two polar extremities, 

 however, remain uncovered by this investment, and at these 

 points the internal membrane of the egg projects as a short 

 rounded appendage. The Reporter has observed the ova of 

 the Trichosomata from the Dog and Seagull to be formed 

 exactly in the same way and also the ova of the Tricho- 

 cephali. From Dujardin's assertion it would appear that 

 the ova of Trichosoma cyprinorum are externally horny, and 

 those of Trichosoma soricum surrounded with a mucous 

 layer, by means of which they adhere together in masses. 

 In the Trichosomata of the Shrew-mouse, respecting which 

 Dujardin leaves it doubtful whether those found in the 



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