196 



EMBRYOLOGY 



The Cysticercus may remain for a longer or a shorter time 

 in the condition described, but may increase meantime in 



^^iii- 



Fig. 96.—^ to H, development of tlie tapeworm from embryo to scolex (after 

 LEtrCKAitT). ^, six-hook embryo ; B, Cysticercus of Tterija sngtnata ; C to -E, cephalic 

 process of the hydatid {Cysticercus 'püiformia) of T. saginata: C, before the funda- 

 ments of the suckers and hooks have made their appearance, D, with fundaments 

 of the hooks and suckers, E, in the partially evaginated condition ; F, fully evagi- 

 nated cephalic process with attached vesicle of T. aolimn ; G, scolex of T. serrata 

 with the remains of the vesicle, which has fallen away ; H, young tapeworm (T. 

 serratii), which has only just left the scolex stage, and in which there are therefore 

 only a few segments. 



vertebrated animals, especially in Crustacea (e.fi. Gammarus and Cyclops), 

 are very noteworthy ; their relationships, however, are not yet sufficiently 

 understood. The caudal appendage, which sometimes attains a very 

 considerable length, carries about with it the remains of the embryonal 

 envelopes. This stage in the development of the Cestodes thereby 

 acquires to a certain extent the appearance of a Cercaria. Such tail- 

 bearing Cysticerci, which belong especially to the genus Taenia, have 

 been repeatedly discovered in recent years, and carefully studied by 

 Hajiann, Mrazek, and Geassi e Rovelli (see A^jpendix to lAterature on 

 Cestoda).— K.] 



