based on the principle of Cephalization—lInsects, 29 
B. The grand subdivisions of Insecteans are Insects, Spiders, 
and Myriapods. 
assing from Insects to Spiders, the methods of decephal- 
ization illustrated are the retroferent, case a, in the transfer of one 
pair of mouth organs to the locomotive series; and ashadeof the , 
analytic, in the loss of the independent definition of the head 
and thorax. 
Pterometasthentes, and Thysanures or Apters. ae 
_ In passing from the first to the second, the principal method 
illustrated is the retroferent, case b, as shown in the transfer back- 
ward of the flying function, and also in the locomotive function 
cae transferred in a considerable degree from the wings to the 
eet. 
In passing from the second to the third, the methods exempli- 
fied are the analytic, shown in the equal annuli and partial loss 
of distinction of thorax and abdomen; the retroferent, case b, in 
the transfer backward to the caudal extremity of a part of the 
locomotive function ; elliptic, in the absence of wings; prematu- 
rative, in there being no metamorphosis. 
rand subdivisions of the Pteroprosthenics are the 
ters, Dipters and Aphanipters. 
_F. The grand Micaak' of the Amplipens are Lepidopters, 
Homopters and Trichopters. é 
In passing from the /irst to the second, the methods exemplified 
