176 
Development of Hook-worms 
this difficult point. He remarks on the difficulty himself and mentions 
the fact that several free-living and larval nematodes may frequently 
be found on the surface and in the intestine of fly maggots. If these 
larvae can be swallowed by the fly maggots there appears no reason 
why the same should not occur with hook-worm larvae. The point 
to be considered, however, is the ultimate fate of these larvae. It must 
be remembered that Habronetna and Anhylostoma belong to widely 
different groups of nematodes, the former of which usuaUy requires 
an intermediate host, while the latter has none. It is, therefore, 
impossible to draw any analogy between the behaviour of Habronema 
larvae in'the fly and the larvae of Ankylostoma, for if Ransom’s view 
*be correct, the fly is the natural habitat of the former. 
II. In the second series of experiments the effect of common salt in 
the solid state was investigated. The salt was simply sprinkled on the top 
of the faecal material. An average sample of the faeces was found to 
contain 71 % by weight of moisture. The quantities of faeces and salt 
used in each experiment were weighed. It was found most convenient 
to employ 3-5 grammes of faeces while the quantity of salt used varied 
from 0-4 to 9-1 grammes. The proportion of salt to faeces varied from 
1 : 10 to 30 : 1 and the proportion of salt to solid matter in the faeces 
varied from 3 : 10 to 10 : 1. 
As 1 c.c. of water will only dissolve about 0-36 gramme of salt and 
therefore 1 gramme of faeces can only absorb about 0-25 gramme of 
salt it is obvious that all the salt used in the experiments at the extreme 
end of the series could not possibly be absorbed by the faecal moisture. 
Thus in one experiment eleven times as much salt was used as could 
be absorbed, and therefore the bulk of the salt only acted as a covering. 
Even with the enormous quantities of salt, however, occasional living 
eggs could be found in the faeces after 24 hours and larvae could be 
hatched from them although their growth was greatly retarded and they 
usually died very quickly. Apparently the salt was absorbed extremely 
slowly and did not thoroughly permeate the faecal mass till more than 
24 hours had elapsed. 
With another sample of faeces, however, containing slightly more 
moisture (72-3 %), 1 gramme of salt sprinkled on 2 grammes of faeces 
was found to arrest the development of the eggs completely within 
24 hours. When half the quantity of salt was added the eggs survived 
for one day but not for two days, while when the quantity was reduced 
to one-quarter (1 gramme to 8 grammes) the eggs lived for two days 
