Internal Organs. 
831 
The organs situated in the head are greatly crowded together, 
by reason of the lateral flattening of the head, and its very 
short antero-posterior axis. Intestine, brain, and eyes are 
closely pressed together. The general form and arrangement of 
these organs can be seen in PI. XIV, Fig. 4. The eye is of 
moderate size, and shows about eight lenses, which do not pro¬ 
ject far from the pigment. Its muscles number, as usual, three 
on each side, and are very short. The optic ganglion is so 
close to the the eye that the optic nerves are hardly visible. 
The brain is of usual size, pear-shaped as seen from the side, 
and has a stout projection extending to the macula nigra. This 
structure lies at the apex of the rostrum, is quadrangular in 
form as seen from the side, and is of ordinary size. A curious, 
pear-shaped little body, (Fig. 4, a.) very transparent, and appar¬ 
ently without definite structure, lies in the apex of the rostrum. 
It has the appearance of a large eve-lens, but does not seem to 
be related to the pigment spot, though it is attached to the nerve 
of the antennule. The antennulary nerve develops the usual gan¬ 
glion in the antennule, and calls for no special description. 
The dilator muscles of the oesophagus are quite distinct, and 
easy to make out. They appear to be in two groups, of about 
four muscles each, on each side of the oesophagus. The muscles- 
of each cluster converge, and are attached to the side of the 
head. 
There is a large labral gland, as usual, but the greater 
part of the crest of the labrum is empty, showing a clear 
space. The elevator muscles of the labrum occupy the ordinary 
position. 
The shell gland, on the whole, recalls the form of that organ 
in the Lynceidoe. It is long, narrow, and developed into a 
round loop at the ventral end. 
The figure shows one of the mamilliform processes, of which 
there may be three or four. These are probably of use in fur¬ 
nishing nutriment to the developing young. They occur also 
in Macrothrix. 
The ovaries call for no special remark. The summer eggs 
number 6-8, are of an elongated oval form, and have a bright 
green, yolk. 
