IV. NEMERTINA 



2.55 



cellulose of T. solium, found in man, more frequent and of more importance is 

 the cysticercus of Tamia echinococcus (fig. 232), which lives as an adult in the 

 dog, and is easily overlooked on account of its size. It is at most i inch long 

 and consists of a scolex and three or four proglottids. When the eggs are taken 

 into the human stomach, as may easily happen by stroking and kissing infected 

 dogs, the embryos are set free and wander into liver, lungs, brain, or other organs 

 and produce here tumors which, in the case of the liver, may weigh ten or even 

 thirty pounds. This extraordinarv size is explained by the formation of 

 daughter bladders (echinococcus) described above. 



Fig. 234. — Heads and proglottids of three tapeworms of man. Left, Tmtia sagi- 

 nata; middle, T. solium; right, Bothriocephalus la/us, flat and side view of head. The 

 heads enlarged about six times, the proglottids about ih (after Leuckart, Braun, 

 and Schauinsland). 



Common Tccnix of domestic animals are in the horse Anoplocephala plicata 

 (4 to 30 inches), A. perfoliata [^ to 3 inches), A. mamillana (J to 2 inches); 

 in ruminants, Moniezia,''' in the dog, Tania marginaia* (cysticercus in sheep 

 and swine), T. serrata* (cysticercus in rabbits), T. echinococcus (above), T. 

 ccenurus (cysticercus in brain of sheep, causing the disease called 'staggers'), 

 DipvUdium cticumerina* (most common, larva in the flea and dog-louse); in the 

 cat, Tccnia crassicollis'^' (cysticercus in mice). Several species occur in domestic 

 birds, one {Drepanidotcenia infimdibuUformis*), causing epidemics among 

 chickens. Others in ducks and geese. 



Class IV. Nemertini. 



Most nemerteans are of appreciable size, some reaching a length of a 

 yard or more (Lineus loiigissimus 90 feet !) , and yet they are so contractile 

 that our Cerehratulus lacteus, which can extend itself to fifteen feet, can 

 retract to two. Nemerteans are rare in fresh w^ater or moist earth, but 

 are most abundant in the sea, where they burrow through the mud or he 

 rolled up beneath stones. Many are noticeable for their bright colors. 

 Their systematic position is a problem. 



