198 PKOCEEBIXGS OF SOCIETIES. 



or hydatid is to be regarded, as Siebold says, as an abnormal 

 dropsical condition ; the creature has lost its way, as it were, 

 and is waitiug to be removed by the mastication of some 

 carnivorous animal. The restriction of the existence of 

 species of tape- worm to certain stomachs is very noticeable. 

 The pig's stomach will not support its (the human) cysticerci. 

 Lecture VII. — Van Beueden's classification of Cestoidea 

 was considered very good by Professor Huxlev. 1. Carvo- 

 phyllidea : simple forms found in the carp, of only one joint 

 and an unarmed head. 2. Tetraphyllidea : found in sharks 

 and rays, whilst the pupge live in osseous fish ; they have 

 very complete hooks, and four probosces like tli^t of Echino- 

 rhynchus. 3. Diphyllidea : contains the single genus, Echino- 

 bothriiim, also found in Plagiostomous fish. 4. Pseudo- 

 phyllidea : with no suckers, and but- few hooks, not in a 

 circle. To this group belongs Ligula, common in fresh-water 

 fish. The imago is found in water birds, Ligula is band- 

 like, and unsegmented in appearance, but contains many 

 series of reproductive organs. Bothriocephalus belongs here. 

 In Eussia, Poland, the Baltic, Switzerland, and Ireland, it 

 occurs as a human parasite. Fresh-water fish have been 

 supposed to be the means of introducing it. The larva, 

 unlike that of any other Cestoid, is ciliated. The genital 

 pore is in the middle of each joint of the adult worm, and 

 the uterus is coiled. 5. Teeniada : almost exclusively as 

 adults in the mammalia. The differences presented by the 

 group are greatest in the pupal state; there is the Cysti- 

 cercus, the Coenurus, and the Echniococcus form. The com- 

 mon tape-worm is not T. soUum, but T. mediocaneJlata, 

 which has no hooks. Its hydatid or pupa harbours in the 

 ox. A man who liked mutton seemed in spite of this 

 discovery to be safe, but now, alas ! a hydatid has been 

 found in a mutton chop.^ The Cysticercus form of larva 

 is a bag, with a single small hooked head, which becomes 

 the tape-worm head. Coenurus has many of these heads, and 

 is a much larger sac ; they are found in the brain of sheep, 

 and as the heads are hooked and retractile cause considerable 

 cerebral disturbance. The tape-worm of the Coenurus lives 

 in the sheep-dog. The terrible Echinococcus, which some- 

 times forms cysts in the human liver, has a disputed structure. 

 Its tape-worm is very small, and lives in the dog, having only 

 three joints. Professor Huxley some years since had the 

 opportunity of examining an Echniococcus cyst from the 

 Quaggaj and he now described it in some detail. The first 



* Horse seems after ail the only food that can be relied on. 



