670 DESCRIPTION OF TJEXIA. CUCUMERINA. 



without a proper caudal bladder. It is true that the entire attaching 

 apparatus, including both suckers and rostellum, was retracted, but the 

 envelope of the latter did not differ either morphologically or histo- 

 logically from the rest of the body. The Cysticercoid appeared exactly 

 like an chinococcus-hQa,d with a retracted apex. 



The intermediate host of Tcenia ciwumerina having been dis- 

 covered, 1 it occurred to us that it might be possible to rear its Cysti- 

 cercoids. A pulp, made of the ripe joints of the Tcenia, was by my 

 advice applied to a portion of skin upon which the Trichodedes were 

 plentiful, and afterwards the first stages of the worm were sought 

 for in these insects. These we succeeded in finding on several occa- 

 sions, and for the first time seven days after the commencement of 

 the experiment. They were in the form of club-shaped, six-hooked 

 embryos, which had attained a length of 0'2 mm. double their former 

 size, and lay free in the body-cavity. Eegarding their origin, there 

 could be no doubt from the six hooks still situated at the thinner end. 



A comparison with the above-described Cysticercoids seems to 

 suggest that the distended end of the body in this case becomes pro- 

 vided with hooks, and is then retracted into the dependent thinner 

 part, but without the latter being formed into a special bladder-body, 

 or producing the tape-worm head by endogenous budding. I may 

 refer in this connection to the description which I have already given 

 of the mode of development of the Tcenice (p. 364). 



These results reveal to us clearly and explicitly the life-history of 

 Tcenia cucumerina. The egg-capsules, which have probably been long 

 preserved from desiccation, and have retained their power of develop- 

 ment, make their way sooner or later (sometimes still enveloped by 

 the proglottides, and at other times alone) from the excreta to the 

 hairy skin of the dog, and thence to the Trichodectes living upon it, 

 in the interior of which the eggs change into Cysticercoids. It is easy 

 to see that dogs, which, like other animals, often lick themselves, and 

 also directly prey upon their vermin with their lips and teeth, often 

 find opportunities of devouring the hosts of these bladder-worms, and 

 of course the more frequently the more that their condition and mode 

 of life facilitates the transmission of the eggs, and the increase of the 

 ectoparasites. Uncleanly kept house-dogs thus exhibit a peculiarly 

 favourable combination of the conditions necessary for the develop- 

 ment of Tcenia cucumerina. 



The infection of man takes place, as might be supposed, either 

 through the tongue of the dog, which returns caresses by licking, or 



1 This demonstration, of course, showed that the former conjectures regarding the 

 intermediate host of Tcenia cucumeiina (see first German edition, Bd. i., p. 404) were 

 illusory. Even then, however, it seemed very likely that the latter would be an insect. 



