Helmintha < 



A Study of One of the Distomes. 87 



Yet in Iceland, a cestode causes the death of the third part of 

 the population, and we are all aware of the excitement 

 Trichinae have produced. 



8. They are not easily killed. Some can be dried completely 

 and returned to life by moistening. Eggs preserved for years 

 in alcohol, chromic acid, and other destroying agents bring 

 forth embryos when placed in proper surroundings, such as 

 water or damp earth. 



9. They have a great tendency to roam ; " Migration is the 

 very soul of their prosperity." 



The parasite under consideration is found in the bladder of 

 the frog ; and in order that we may understand the position 

 he holds among the Helmintha, we append the following 

 standard classification : 



f Turbellaria 



Sterelmintha J {Order I.) 



(^Sub-Class I.) ) Trematoda "^ 



L {Order II.) 



Coelemintha \ Nematoda | 



iSub-Class II.) -{ {Order III.) I j-^^^^ 

 f Acanthocepala f ^"^ozoa. 



Anenterel'mintha j {Order IV.) j 



[^ {Sub-Class III.) ") Cestoda | 



I {Order V.) J 



The first sub-class is characterized by having solid or hard 

 bodies ; the second, by having hollow or cavitary bodies ; and 

 the third, by not being provided with an intestinal canal. 



The Sterelmintha, we see, are divided into two orders : 



1. Turbellaria, having ciliated epithelium covering the entire 

 body, and receiving their name because of the peculiar rota- 

 tory motion communicated to the water as they swim through 

 It. 



2. Trematoda, which, as their name suggests, are character- 

 ized by certain holes or pores. 



It is to the latter order that we must give our especial at- 

 tention. They are, as a rule, visible to the naked eye, ranging 

 from .25 mm. to 6 and 8 centimeters in length. Thus viewed, 

 there is nothing about them to attract attention ; but upon 

 closer examination, bringing the microscope to our aid, we are 

 astonished at their beauty and the complexity of their organi- 

 zation. They are not parasitic during their whole lives, for we 

 find them at certain periods of their existence inhabiting low, 

 moist grounds, and open waters. There are about 400 species, 

 yet rarely are they found in man or monkeys. None have 



