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 zoologists 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 formulas 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 



