206 Remarks on Parasites. 



This extraordinary power of reproduction would be quite as 

 superfluous in them, if spontaneous generation were possible, 

 as it appears to be necessary, if they are to be continued by 

 sexual reproduction, in situations where they are exposed to so 

 many injurious influences. 



2. The entozoa during their development, assume various 

 forms differing much from each other, some one of which 

 seems to be suited for their living out of the body, or at least 

 to facilitate their passage, from one body to another. 



3. The entozoa wander through the body which they in- 

 habit, as well as through its surrounding media. Their 

 easiest and shortest way to reach the internal organs, is 

 through the skin or perhaps also through the blood vessels* 

 at all events there is no doubt as to the fact that they can 

 live in the blood. 



4. Most of the intestinal entozoa are very tenacious of life, 

 and after being dried, can be again awakened to life by the 

 application of moisture. 



5. The occurrence of certain intestinal worms only within 

 certain defined districts, is an indication of their having a de- 

 finite distribution. Instances of this are, the occurrence of 

 Bothriocephalus latus and Tania Solium — in individuals who 

 have resided for a time in localities where they are endemic, 

 or the production of dry rot in sheep by pasturing them on 

 marshy ground, &c. 



It is no doubt true that there is a class of internal parasites, 

 which until lately could not be shewn to multiply themselves 

 in the same way as those already alluded to ; namely, hydatids, 

 and in which neither generative organs nor ova had been re- 

 cognised, and it is on them chiefly that the supporters of 

 equivocal generation rely. But the recent researches of Klencke 

 seem to place it beyond doubt that hydatids multiply by ova, 

 like other animals. 



