656 ORDINARY TAPE- WORMS (CYSTOIDEl). 



and form small independent brood-pouches, filling the middle layer 

 of the joint, varying in number and arrangement. The structure of 

 the germ -producing organs exhibits also numerous variations, which 

 are in part so fundamental and characteristic that various attempts 

 have been made to utilise them for systematic purposes. We have 

 already noted many of these peculiarities, but we may shortly revert 

 to them. Sometimes the female reproductive organs recall exactly 

 the structure of the cystic tape- worms, while the testes are but 

 sparsely developed, being, indeed, sometimes reduced to two or three. 

 On the other hand, the male and female spermatic reservoirs and the 

 cirrhus often attain a considerable size. The generative openings 

 usually lie all on the same margin, but are occasionally found on 

 both sides. The eggs have besides the thin light-brown shell, and 

 the very constantly persistent vitelline membrane, not unfrequently a 

 third middle envelope. Where the uterine cavity is broken up into 

 distinct brood-pouches, as is the case in the Cystoidei of man, then 

 all the contained eggs of the latter are during the formation of the 

 embryos united into a single mass, which is in some respects com- 

 parable with the cocoon of the leech or earth-worm. The embryonic 

 hooks are often of considerable size, and are in some cases larger than 

 the hooks of the adult worms. 



We cannot yet determine with certainty how many human tape- 

 worms belong to this group. As yet we only know four, but these 

 have all been lately discovered, and the number will doubtless be yet 

 increased. This is the more probable, since, with one exception, these 

 worms belong to foreign countries, where helminthology has been little 

 prosecuted, and where the mode of life and nutrition of the inhabitants 

 is in many respects favourable to the importation of Cysticercoids. 



To all appearance, then, the number of cysticercoid Teenies in man 

 is larger than that of the cystic tape-worms ; but none of the former 

 can be compared to the latter in distribution, frequency, or clinical 

 importance. It seems even doubtful whether any one of them is 

 peculiar to man. The species indigenous in our country, 1 Tcenia 

 cucumerina, is certainly not, for it is usually found in the dog and 

 cat, and only occasionally in children. 



According to their natural relationship these worms belong to 

 various groups, the members of which are probably in every case con- 

 fined to the Mammalia. 



1 We must leave it as undecided whether the smooth-shelled T&nia-eggs found by 

 Ransom in the faeces of a child belong to a second European species (Medical Times, 

 vol. x., p. 598, 1856). The same must be said of Heller's report, according to which the 

 Erlangen Pathological Institute contains a Tcenia as yet unidentified, which was voided 

 by a child (Zieinssen's " Handb. d. sp. Path. u. Ther.," Bd. vii., p. 560) ; Eng. transl., 

 vol. vii., p. 670. 



