INTRODUCTION. XV 
In some parasitic families these organs undergo an 
extreme amount of modification. This is much more 
exaggerated in the Jsopoda than in the Amphipoda. 
Among the Cyami, the oral appendages are all reduced 
and somewhat modified, but in the Cymothoide, Bopyride, 
and Anceide, among the Jsopoda, they appear to lose 
much of their normal character, and fulfil the office of a 
sucking apparatus. In the formation of this organ one 
or more pairs of the appendages may be implicated, as 
is shown in an elaborate memoir by Schiddte* on the 
subject. The manner in which the organ is developed in 
Jone from the mandibles, we have described at page 253, 
vol. 11. of this Work. 
In the Anceide, the appendages of the mouth in the 
young stage are sharp and lanceolate, the sucking organ 
being apparently modified from the labrum, where, as 
in the adult animals, the oral aperture, with the sup- 
plying appendages, are lost, or converted into members 
useful for other purposes. 
In the genus Brachyscelus, and others of the family 
Platyscelide, the appendages of the oral apparatus are 
reduced to a single pair of membranous leaf-like organs ; 
nor have we been enabled to trace any different character 
of organ to take the place of the lost ones. Both in the 
adult and young animal, the mouth appears to be reduced 
to a rudimentary and simple character: an aperture with 
the probable power of opening and closing at will being 
the most that we have been enabled to determine. 
The first or anterior maxillee (Siagnopoda) are separated 
from the mandibles by a posterior lip, which differs in the 
Amphipoda—or at least in some genera—in being cleft lon- 
gitudinally in the median line, and is termed the labium ; 
* Natur. Hist. Tidssk. 1866, p. 168—206. 
