54 LECTUKE IV. 



velopment of the organs of generation. During winter the Bothrio- 

 cephalus punctatus, still adhering firmly to the mucous surface of the 

 pyloric appendages, grows to its full length, and the generative organs 

 are formed ; but no ova can be seen. These begin to appear at the 

 commencement of spring in the posterior joints, and by degrees fill 

 the uteri of all the joints, until they occupy those which are close to 

 the head, when the separation from the head before described en- 

 sues, and this last-named member is left to repeat the important 

 process. 



No single joint of a tapeworm can develope a head, and form a 

 new individual ; the transverse fission relates only to the dissemination 

 of the fertile ova, from which alone new TcBiiice. are developed. 



The hypothesis of equivocal generation has been deemed to apply 

 more strongly to the appearance of internal parasites in animal bodies 

 than to the origin of animalcules in infusions. But if a tapeworm 

 might be organised from a fortuitous concourse of organic particles, 

 or by the metamorphoses of an organic cell in the animal it infests, 

 why that immense complication and extent of the organs for the 

 production of normal fertile ova ? 



" The division of the body into joints is intended," as Professor 

 Eschricht well observes, " to produce a corresponding number of 

 bunches of ova, just as the repeated ramification of plants is destined 

 to provide space for the production of new bunches of seeds." The 

 head of the tapeworm is fixed to the mucous surface, and thence it 

 derives the nutritive juices required for the whole organism ; in the 

 same manner as the root procures the nourishment of the plant from 

 the soil. The ova having reached maturity, the joints rupture to 

 liberate them ; or the whole joint will be thrown off" in the same way 

 as the seeds of plants are freed, sometimes one by one, sometimes in 

 masses, according to the particular manner of life assigned to every 

 species of plant. " And is there any one," asks Dr. Eschricht, " who, 

 upon the contemplation of this wonderful apparatus, and the ex- 

 traordinary results of its agency, can for a moment imagine that it is 

 without an object or an end?" 



The geographical distribution of the human Cestoidea is, likewise, 

 opposed to the doctrine of their spontaneous origin. The organic 

 particles, or alimentary mucus of a Swiss and Dutchman, are not so 

 distinct in their nature as to account for the difi'erence in their tape- 

 worms. A native of one of these countries may be infested by the 

 tapeworm peculiar to another region, if he sojourn there, just as 

 the English sailor may be attacked by the Guinea- worm, if he visits 

 the tropical regions where that entozoon is common. 



The great anatomist Soemmering suffered from a Bothriocephalus 



