234 ANIMAL PARASITES AND MESSMATES. 



thology than any other naturalist, brought together, 

 under the name of Agamonema, all the migratory 

 agamous nematodes which wait for the opportunity of 

 entering their final host. Diezing had kept himself 

 quite independent of the discussion by fixing his atten- 

 tion exclusively on form, without taking account of 

 migration and digenesis. One of these agamonemata, 

 lodged in the midst of a pediculated cyst on the vagina 

 of a bat (the little horse-shoe), was probably a worm that 

 has lost its way ; if not, we must admit that these 

 mammals become the prey of some carnivorous animal. 

 But what carnivore can habitually feed on the cheirop- 

 tera ? There are but few fishes, either in fresh or salt 

 water, which do not enclose in the folds of their perito- 

 neum, especially round the liver, cysts full of these 

 agamonemata. 



We see in some of the nematodes examples of migra- 

 tion which are quite peculiar to them. Some of these 

 worms are always free, others free at one part of their 

 life only, others migrate from one animal to another; 

 others again from one organ to another. The Ascaris 

 mgro-venosa of the frog lives sometimes in the lungs, at 

 others in the rectum or quite out of the body in damp 

 earth. The Filcuria attenuata lives in' the rook (Corvus 

 frugilegus), and it is said that it becomes sexual in the 

 intestines of the same bird. 



These worms are usually very tenacious of life; 

 many of them can, it is said, be dried for weeks, months, 

 or years together, and return to life as soon as their 

 organs are moistened. Their eggs resist even the action 

 of alcohol and the most active chemical agents, and eggs 

 that had been prepared for the microscope, and had 



