ENTOZOA. 53 



beneath tlie skin at the sides of the joints. Eschricht calculates that 

 there are 1200 of these glands in each joint. In the joints furthest from 

 the head, containing the mature ova, these glands become filled with 

 a thick yellow matter which they pour into a system of ramified 

 ducts, which unite to discharge themselves in the dilated part of the 

 uterus. Their office seems to be to cement together the ova in hard 

 cylindrical masses by forming a crust around them, in which state 

 they are found in the detached joints. This is the first example 

 which we have yet seen of nidamental glands, which we shall sub- 

 sequently find a conspicuous part of the generative organs in many 

 oviparous Invertebrata. 



From this description it will be seen that the proportions and 

 almost the forms of the ovarium and testis, are reversed in the 

 Bothriocephalus and Tcenia : the positions of the sexual outlets 

 are unquestionably very different in the two genera. Both, how- 

 ever, agree in presenting the most extensive development and pre- 

 ponderance of the generative system that is known in the Animal 

 Kingdom. In fact there is scarcely space left in the hinder joints 

 of the tapeworms for the organs of any of the other systems. 



The natural rate of life of a tapeworm, the consequences to the 

 remaining adherent part of the repeated detachment of the ovi- 

 gei'ous segments, the extent to which they are detached and subse- 

 quently renewed, have not yet been, nor are likely ever to be, the 

 subjects of direct observation in these internal parasites of man. 



Some highly interesting facts have, however, been made known by 

 the same professor to whom we are indebted for a knowledge of the 

 anatomy of the Bothriocephalus latus, in the economy of another 

 species of Bothriocephalus which is extremely common in the small 

 sea-fisii called Cottus scorpius. 



During midsummer, these tapeworms are fully developed, and 

 their segments are laden with ova. They adhere by the fore part of 

 the head to the mucous surfaces of the appendices pyloricfE, and cast 

 off the ovigerous segments, sometimes in their whole length ; so that 

 headless tapeworms are found in the lower part of the intestine, 

 whilst a number of heads without bodies may be observed adhering 

 to the pyloric appendages between other tapeworms of very different 

 lengths. The heads thus left behind generate a new series of perfect 

 joints in the following way : the joint next the head is divided by a 

 transverse fissure into two, each of which repeats the same process 

 as soon as it is somewhat grown. Whilst the joints multiply in this 

 way, they continue to increase in size, and so become removed from 

 the head ; but at a certain distance from the head, this mode of sub- 

 dividing ceases, and tiie whole nutritive power is applied to the dc- 



E 3 



