C. L. Boulenger 
153 
6. The sheaths are cast off by the larvae when these are subjected 
to temperatures approximating to the blood-temperature of the host; 
completion of the second moult occasionally also takes place at laboratory 
temperatures under certain abnormal conditions. 
7. No infection experiments were made on sheep, but other evidence 
shows that these animals must become infected by swallowing the 
sheathed larvae, either when free or whilst still enclosed in the egg¬ 
shells. 
8. A number of young stages of the parasite were met with in the 
intestines of sheep, the smallest of these being only little more advanced 
in structure than the larvae just after ecdysis. 
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