IN THE BODIES OF ANIMALS. 391 



water, they easily might find access to the interior of a great 

 variety of animals, which certainly has not been observed. 



I must confess that I am astonished at the third argument 

 brought forward by this great man, for it is diametrically opposed 

 to his hypothesis. " It is impossible that worms discovered in 

 the foetus in utero can owe their existence to ovules derived 

 from without, since there is no external communication." 



But in addition to these objections to the hypothesis, there are 

 abundance of others, and those too of great importance; I do 

 not deny that many of the eggs of worms, living in the ali- 

 mentary tube, may pass out with the feeces, but I feel 

 persuaded that they rapidly die. The great number of eggs 

 existing in one worm does of itself present a great obstacle to 

 their being all expelled ; and, in order that they should not all 

 perish, they are made to abound to such a degree that some of 

 them at least should find a congenial settlement. That they 

 are capable of maintaining life whilst under the influence of 

 air is highly improbable, seeing that it rapidly destroys the 

 worms themselves, rendering them stiff and dry: — would the 

 tender ovules be less susceptible of such influence ? And if 

 we could form a conception of the myriads of eggs and seeds 

 which the imaginations of authors have wafted into our atmo- 

 sphere, we may well smile, for they had formed a large part of 

 its constitution. 



As the eggs of worms found in warm-blooded animals re- 

 quire the same degree of temperature as the parents, I can 

 hardly think it possible that the germs could be preserved 

 alive in so cold a medium as water. But even allowing that 

 the ovules are capable of supporting life under all the cir- 

 cumstances of extrinsic existence, it still remains a question, — 

 How do they reach those regions of the body which some 

 of them are known to occupy ? That they are of too large 

 a magnitude to pass by the small vessels I shall prove pre- 

 sently, and these are the only media through which they 

 can arrive at the brain, the liver, and some other situations. 

 As great a difficulty involves the solution of the question — 

 By what means are they transported from these situations into 

 the water, air, &c. ? Lastly, How does this doctrine apply to 

 those Entozoa which lead a solitary life enclosed in a cyst, 

 unprovided with the means for copulation, and in whom there 

 is no vestige either of genital organs or eggs ? If, however, it 



