172 J. D, Dana on Cephalization. 
its force-system attained thus a 1-horse capability when the en- 
gine had attained the size of a 100 horse-power, and poor con- 
struction with that. What would it be but a small thing vastly 
overgrown. In an animal there are the sensorial and motorial 
movements, or by stupid senses, and have corresponding struc- 
tural deficiencies: as is true of a huge Medusa among Radiates, 
a Horse-shoe (Limulus) among Crustaceans; a Sloth and its kin 
among Mammals, etc., ete. 
of structure in fixing the limits of natural groups. Toward this 
latter object it affords aid through the many new criteria It 
brings to light, and through the evidence it supplies as to the 
relative value of such criteria; yet its distinctions are to used 
in connection with all others that are available. And they have 
been thus used by the writer in his attempts to present the true — 
system of arrangement amon ies. 
I have been led to place the Homopters near the Lepidopters, 
and the Hemipters near the Coleopters, by the following consid- 
erations :—— 
a, The Homopters, as most authors assert, have close structu- 
ral relations to the Lepidopters. The Hemipters are much less 
near the Lepidopters, and approximate, as some authors have ad- 
mitted, to the Orthopters and Coleopters, especially the former. — 
The fact that the anterior wings in Hemipters, as in the Co 
ters and Orthopters, are not flying wings, is an important point = 
\ 
2S PS Seppe eee, 6 Sean NE ad aaa 
