CE5TODE5 35 



species. The segments adjacent to the head are immature the sexually mature 

 ones being found from the middle of the body onward. 



T. sagifmia has about 2000 segments, T. solium less than 1000 whfle T. eckino- 

 coccus has only three or four. The sexually mature segment possesses a varying 

 number ol testicles: three in Hymcnolepsis nana and as many as 2000 in Tcrnia 

 sagittate. As with the flukes, they also have vasa deferentia, cirrus, ovaries, yolk 

 glands, uterus, genital pore, etc. The location of the genital pore and the charac- 

 ter of the branching of the uterus are of the greatest importance in differentiation. 

 The sexually mature proglottides may either expel their ova, when these would be 

 found in the faeces or, as is common, they break off and pass out themselves in the 

 faeces. Then they either expel the eggs or may be eaten by some animal and in 

 this way effect an entrance for their ova. It is an important practical point that 

 the faeces of a patient with T. solium or T. sagittate may not show any ova, these 

 passing out in the intact segments. The oval operculated eggs of Diboikriocephalus 

 lotus, however, are constantly in the faeces. 



The "hexacanth" or six-hooked embryo, also called the onchosphere, is the essen- 

 tial part of the egg. The embryonic envelope is dissolved off in the alimentary 

 canal of the animal ingesting it, and the onchosphere bores its way through the gut 

 to later become encysted in various tissues. In some tape- worms a ciliated embryo 

 is liberated from the egg shell and swims about actively to enter some fish or other 

 animal. When the six-hooked embryo reaches its proper tissue, the booklets are 

 discarded and a scolex similar to the parent one is developed. At this time we have 

 a bladder-like structure with the scolex inverted in it. This is termed the proscolex 

 stage. This Kttk cyst with its scolex when ingested by another animal is digested, 

 and the sccdfr, establishing itself in the intestine, develops a series of segments. 

 The ciliated embryo of the D. lotus does not form a cyst, but instead a worm-like 

 creature q'milar to the adult. This is termed a Plerocercoid. 



If the larval stage shows a single cyst and a single head, it is termed 

 Cysticercus; if multiple cysts but only one head to each cyst, Ccenwrus; 

 while with multiple cysts and multiple heads hi each cyst the term 

 Eckinocvccus is used. 



Where there is very little fluid in the cyst and the larva is of minute 

 as with the HymenoUpsis, the term Ccrcocystis is employed. 



KEY TO CESTODE GENEEA 



I. Head with two elongated sfit-Kke suckers Genital pores ventral Rosette 

 uterus. Dibothriocephabdae. 



(A) Single set of genital organs in each segment. Dtbotkrioccpkalus. 



(B) Double set of genital organs in each segment. Dipbgottoporus. 



(O Immature forms showing characteristics of Dibothriocephalidae (collective 



group). Sparganum. 

 II. Head with four cup-like suckers; genital pores lateral Taeniidae. 



(A) Uterus with "M^Kaii stem and a varying number of lateral branches. Tctnia. 



(B) Uterus without median stem and lateral branches. 



