based on the principle of Cephalization. 335 
all, more regular or normal in form. 
+ 
analytic, also, the lengthened abdomen in the Macruran has its 
normal number of segments and members. 
Among the subdivisions of Macrurans, the retroferent method 
appears prominently in the transfer of force from the first pair 
of legs to the second and, among the lower genera, to the third 
pair (see p. 823); the amplificative, in the length of antenne in 
some families, and in the Jength of abdomen as compared with 
that of the cephalothorax in others; the elliptic, in the absence of 
rurans. 
Under Tetradecapods, the difference between the Ist and 2nd 
tribes, or Isopods and Amphipods, depends on the very same 
methods as that between the Ist and 2nd under the Decapods: 
the lengthened abdomen having its normal segments and ap- 
proximately normal members. : ; 
_ Under the Amphipods, the amplificative method is ee 
illustrated ; the elliptic in the obsolescent abdomen of the Caprel- 
lids, as well as in the absence or obsolescence in many species of 
