ie) 
348 PROFESSOR E, RAY LANKESTER, 
faee is vertical to the ventral surface of the animal, and at 
right angles to the antero-posterior axis. It is provided 
with numerous lamelliform processes. The median portion 
may be spoken of as the axis or corm, whilst the processes 
may be called “ phyllites” or “apophyses,” those ranged 
along the ventral or neural border of the corm being called 
“ endites,”’ and those given off from the dorsal border being 
called “ exites.” There are six endites, and two exites much 
larger than any of the endites, whilst in front of (distal to) 
the two large exites is a less strongly marked outgrowth of 
the corm, which it will be convenient to call the “ sub-apical 
lobe.” The corm is devoid of segmentation or jointing,’ its 
chitinous cuticle forming one continuous investment to it; 
and moreover, no muscles are inserted into the corm in such 
a way as to cause it to bend upon itself, and so call into 
existence functional, if not structural joints.* 
The cuticle is thin at the base of the corm, where it 
becomes continuous with that of the ventral surface of the 
body, and the movement upon the joint so constituted is 
provided for by powerful muscles, which enter the appendage 
and are inserted into its walls. 
Of the six endites the proximal is somewhat isolated and 
pushed towards the middle line. Its surface is beset with 
powerful sete, and it clearly has the function of assisting, 
by means of apposition to its fellow of the opposite side, in 
seizing and moving particles which may be introduced into 
the mouth. It is a jaw process, and may be spoken of as 
the “‘ gnathobase,”’ It is a fact of no little significance that 
a gnathobase is developed on every one of the sixty-three 
postoral appendages of Apus, especially when we remember 
that a similar feature is characteristic of Limulus, the most 
archaic representative of the Arachnida. 
The gnathobase of the appendage under consideration is 
provided (as is the rule throughout the whole series) with 
powerful special muscles inserted into the corm (see figure), 
but it is not possible to define any arthrodial thinning of 
the cuticle which marks it off from the corm as a distinct 
segment. 
1 Zaddach describes the corm as three-jointed, and Huxley states that 
in Apus glacialus it consists of coxopodite, basipodite, and ischiopodite. I 
cannot find any evidence of these joints in the specimens studied by me 
in any of the appendages excepting the first two of the thoracic series. 
2 Such functional joints not indicated by any thinning of the chitinous 
cuticle to form an arthrodial membrane appear to exist at the bases of manv 
of the phyllites in limbs from various parts of the body, and are indicated 
by the insertions of the muscles in the appendages of various erustacean 
Nauplil, as well as in those of the remarkable Rotifer, Pedalion. oe 
