220 ANIMAL PARASITES AND MESSMATES. 



expense, but which has been hitherto found only in 

 Egypt. 



We know perfectly well the itinerary of the Taenia 

 serrata of the dog, which is so abundant, that there are 

 few of these animals that do not enclose some and even 

 many of them. There are few except lapdogs which do 

 not harbour them. We can easily assign the reason. 

 Every tasnia, like every animal, has its eggs ; each 

 plant has its seeds. These eggs are laid by the mother 

 in the most favourable condition for the development of 

 her progeny. The dog deposits its dung on the grass 

 rather than in any other spot, because the eggs of its 

 taenia, which are destined to the rabbits or hares, will 

 have greater chance of arriving at their destination 

 than if they were exposed on the bare earth, or in the 

 water. Their prodigious number is calculated accord- 

 ing to the chances of their arriving safely. The egg, 

 when introduced into the stomach of the rabbit, is 

 rapidly hatched in this organ under the action of the 

 gastric juice, and the embryo which is produced from 

 it seeks its hiding-place in the midst of the tissues 

 which surround it ; it bores into them, and establishes 

 itself in the folds of the peritoneum. Then, once in its 

 resting-place, it barricades itself, and waits patiently 

 for an opportunity of introducing itself into the stomach 

 of the dog. 



This microscopic embryo is armed with six hooks, like 

 embryos of all the cestodes ; it employs them with much 

 dexterity to pierce the walls of the organs, and to hollow 

 out a space for itself in the substance of the tissues. Shut 

 up in its hiding-place, membranes form around for its 

 protection; its six hooks, having become useless, wither; 



