452 



THE ANIMAL PARASITES OF MAN 



oesophagus and the anus in the mid-ventral line. The larva lives 

 on fcecal matter and grows to about 0-4 mm., then moult 1 I takes 

 place in two days or more, the skin being ruptured by the activity of 



the larva. 



Stage II : The larva is now in this stage, which does not differ 

 much from the previous one. It grows to 0-5 mm. The mouth 



FlG. 330. Ancylostoma duodenale larva on fourth day of culture on right ; 

 Strongyloides stercoralis larva on left. (After Leichtenstern.) 



opening closes. The oesophagus elongates, becoming cylindrical or 

 " filariform " ; a new skin is formed underneath the old one, and in 

 about a week moult II takes place. 



Stage III : The mature larva remains enclosed in the old skin. 

 Its movements are now much more active and of a boring character. 

 Length is now o'6 mm. This mature stage has been erroneously 

 called the encysted larva, because there is no cyst secreted from its 



1 Moults take place by the formation of a new skin below the old one, the two being in 

 close apposition at first. 



