130 NEW YORK “ZOOLOGICAL SOCIETY, 
lar tissues, parasites have been found. In fact, scarcely any por- 
tion or tissue of the body is free from intrusion. Parasites be- 
long to such numerous different types that it is quite important 
that the complete dissimilarity of parasitic types and their relation- 
ship to others should be appreciated. 
In dealing with parasites such as certain filaria found in the 
lungs of elk, deer and buffalo, which require an intermediate host 
or bearer, it is important to remember that the existence and grav- 
ity of a parasitism often depends quite as much on the favorable 
conditions of the environment as on the presence of the parasite 
itself. 
Any injurious parasite will tend to increase to a deadly degree 
of prevalence when present in a given locality, in which the num- 
bers of its natural hosts are very great, and in which other condi- 
tions conduce to its preservation and increase. If, for instance, 
it must pass a certain stage (embryo, larva) in water, then wet 
lands, marshes, pools, lakes or sluggish streams are a necessary 
condition. On the other hand, if the larva, as in the case of certain 
tenia (JT. canina), lives in an invertebrate skin-parasite of the 
same host, then the existence and maintenance of the intestinal or 
other parasitism is dependent on the presence of the cutaneous 
parasitism. So with the hundreds of other conditions varying 
with the parasite, the host, and the environment, and, as a rule, 
these conditions must be changed before we can hope to get rid 
of the parasitic invasions. 
Practically all parasites are capable of propagating and devel- 
oping with marvellous rapidity, a single female sometimes pro- 
ducing hundreds, or even thousands, in a very few days. Most 
of them possess inherent vitality, and particularly is this the case 
with the eggs and embryos. They possess the power of resisting 
a certain amount of heat and cold and desquamation, and will even 
withstand some chemical agents. 
During the last year the systematic and regular treatment of 
lions, tigers, leopards, pumas, lynxes, bears, wolves, and foxes, 
and such smaller mammals as badgers, ocelots and other members 
of the Felidz which subsist largely or entirely on a meat and fish 
diet, by administering vermicides and vermifuges at certain reg- 
ular intervals has, in my opinion, been of the greatest importance 
in keeping these animals free from the intestinal disorders so 
frequently produced by intestinal parasites. 
The morbid effects of worms infesting the Canide and Felidz 
cannot be exaggerated. I believe that the epileptiform convul- 
sions or fits, so often seen among young wolves, foxes, ocelots and 
