116 FAMILY CHARACTERISTICS. 
be determined. The great facility with which 
animals may be combined together in -natural 
groups of this kind without any special investi- 
gation of their structure —a superficial method 
of classification in which zodlogists have lately 
indulged to a most unjustifiable degree — con- 
vinces me that it is the similarity of form which 
has unconsciously led such shallow investigators 
to correct results, since upon close examination 
it is found that a large number of the Families 
so determined, and to which no characters at all 
are assigned, nevertheless bear the severest criti- 
cism founded upon anatomical investigation. 
The questions proposed to themselves by all 
students who would characterize Families should 
be these: What are, throughout the Animal 
Kingdom, the peculiar patterns of form by which 
Families are distinguished? and on what struct- 
ural features are these patterns based? Only the 
most patient investigations can give us the an- 
swer, and it will be very long before we can write 
out the formule of these patterns with mathe- 
matical precision, as I believe we shall be able to 
do in a more advanced stage of our science. 
But while the work is in progress, it ought to be 
remembered that a mere general similarity of 
outline is not yet in itself evidence of identity of 
form or pattern, and that, while seemingly very 
different forms may be derived from the same 
