THE ANIMAL PARASITES 629 
The first step in the discussion of the incidence of 
parasites must be that respecting the (host) classes and 
smaller taxonomic divisions — of course as they have been 
studied in this Garden. Certain statistical limitations 
were experienced and can be summarized as follows : 
Data are not available on a sufficiently large number 
of animals to justify conclusions as far down as genera 
and species, except for such commonly and generously 
exhibited forms as monkeys and parrots. I have there- 
fore in tabulating and reviewing our records, distributed 
the animals only as far as families — not into genera and 
species. The table (24) to follow will be found not to 
contain every family because to do so would needlessly 
enlarge it. Accordingly I have followed the policy of 
only indicating those genera and species showing either 
frequent or important infestment. I shall refer to those 
groups later as *' susceptible " groups. If no family 
is recorded in the table it means that we have had no 
important numbers of inf estments in it. The ' ' remarks ' ' 
column shows the individual parasite that has been par- 
ticularly frequent or otherwise important. If there are 
no remarks it means that the species of parasites found 
have been scattering. 
Results of Review and Tabulations. 
We now pass to an analysis and discussion of the find- 
ings brought out in the previously mentioned review of 
our records and in Table 24. Viewed broadly we find 
that there is a wide variation in the susceptibility of dif- 
ferent families to infestment. Those that are susceptible 
may be located by consulting the table, and each will 
therefore not be separately culled out and subjected 
to needless repetition. A few points are however worthy 
of separate mention. While there is a familial or generic 
susceptibility within certain orders it is unwise to gen- 
eralize too broadly. Thus for example the Corvidse have 
