THE CESTOID E A 129 



rose-thorns (Fig. XXIV.) ; genital organs and apertures double in each 

 proglottid (Fig. XXVI.). D. caninum, L. ( = T. cucumerina, Bloch. ; = T. 

 elliptica, Batsch), in the ileum of dog ; cysticereoid in Trichodectes canis and 

 in Pulex serraticeps. The strobila is 100 to 250 mm. long ; the scolex has 

 . four rows of hooklets ; the worm occasionally occurs in man. The larva 

 of D. echinorhynchoides, Sons., occurs in lizards. Hymenolepis, Weinl., the 

 proglottids much broader than long, with the posterior angles projecting like 

 saw-teeth ; genital pores all on the left side ; uterus transverse ; eggs with 

 three envelopes, far apart, the innermost having "horns" (Fig. XXVIII.). 

 H. nana, v. Sieb., in the intestine of man, was originally discovered in an 

 Abyssinian ; it is now known also from Italy, England, United States, 

 and the Argentine. It is about an inch in length ; the rostellum bears a 

 single row of hooklets ; the larva is unknown. H. murina, Duj., in rat 

 and mouse ; the larvae occur in the villi of the intestine, and the adult 

 in the lumen ; there is here, therefore, no change of host ; there is merely 

 a migration from one organ or part of an organ to another. Grassi has 

 suggested that these species are synonymous, but v. Linstow (1895) has 

 pointed out the various differences between them. Drepanidotaenia, 

 Raillet, in the gut of birds, especially aquatic birds ; cysticercoids in small 

 Crustacea. D. infundibuliformis, Goeze, in pigeon and house-fly; 

 Dicranotaenia, Kaill., D. coronula, Duj., duck and Cypris ; Chapmania, 

 Montic. SUB-FAMILY 2. TAENIINAE (= Cystotaenia, Lkt.). Strobila 

 usually of large size ; scolex with two or three circles of hooklets ; 

 uterus median, with lateral caeca ; genital pores, irregularly alternate ; 

 eggs with two envelopes ; the outer thin and deciduous, the inner one 

 thick, brownish, and immediately enveloping the six-hooked embryo. 

 The genus Taenia lias been subdivided into a number of sub-genera by 

 Weinland : Taenia, L. (s. str.), rostellum armed ; larva a cysticercus. 

 T. solium, Kud., intestine of man ; Cijsticercus cellulosae in muscle and 

 viscera of pig, rarely in man, rat, dog, etc. (Fig. XX. 3). Cosmopolitan 

 wherever the pig is a common article of diet, and eaten in an imperfectly 

 cooked condition. Scolex with two circles of hooklets ; strobila 2 to 3 

 metres long, with 850 proglottids, the 450th having fully-formed genital 

 organs. The uterus consists of a median sac, with eight to ten broad caeca, 

 which bear irregular wide lobes. T. serrata, Goeze, in small intestine of 

 dog, wolf, etc., with C. pisiformis in the rabbit and hare ; T. marginata, 

 Batsch, in wolf, butcher's clog, etc., is the largest dog tapeworm, measuring 

 1*5 to 3 metres. Its C. tenuicollis infests the peritoneum, liver, etc., of 

 pig and ruminants. Taeniarhynchus, Weinl., has neither rostellum nor 

 hooklets ; the larva is a cysticercus. T. saginata, Goeze (T. mediocan- 

 ellata, Kiich.), in the intestine of man ; its Cystic, bovis in the muscles of 

 ox (Fig. XX.). Originally from the East, now cosmopolitan, where im- 

 perfectly cooked beef is eaten freely. It measures 7 to 8 metres, and 

 is the largest tapeworm in man; there are about 1200 proglottids, 

 relatively broad, the genital organs being fully formed in the 600th ; the 

 worm appears to be the raiviai of the Greeks. Cystotaenia, Leuck., scolex 

 with two circlets of hooklets ; the larva is a " coenurus." C. coenurus, 

 Kiich., in the ileum of the dog and wolf; Coenurus cerebralis, in the brain 

 of sheep (or other domestic and wild herbivora), swells up to a great size, 



