APPENDAGES AND NERVOUS SYSTEM OF APUS CANCRIFORMIS., 379 
It is quite possible that in Apus, owing to the diminutive 
size and rudimentary character of both pairs of antennz, the 
ganglia appropriate to them have not fused with any others, 
but have entirely disappeared from the lateral cords. This 
possibility is forced upon the attention by the fact that the 
nerve fo the maxillipedes comes off on each side from the 
lateral cord and has no ganglionic enlargement related to it 
(V mp). The mandibles and the maxille have, on the 
other hand, each a perfectly distinct, widely separate pair 
of ganglia (G 2 and G 3), the pairs being connected each by 
two transverse commissural strands. When the thoracic 
region is reached the nerve-cords approximate more closely 
to the middle line, but a distinct ganglion pair is developed 
for each pair of thoracic feet, of which the first only is seen 
in the figure (VI ¢h’). Posteriorly, the ganglia are very 
closely set upon the cords, but, according to the statement 
of Zaddach, there is a distinct ganglion for each of the feet, 
even to the smallest of the abdominal (post-genital) series. 
The facts as to the nervoussystem of Apus which I have above 
cited from Zaddach appear to deserve very serious attention, 
since they tend to show that the nervous system of Crustacea 
consists primarily of an archi-cerebrum and of two lateral 
cords, and that on each cord is a ganglion corresponding to 
each appendage; that the cords tend to meet one another in 
the middle line; that when appendages become rudimentary 
(e.g. the maxillipedes) their ganglia may disappear ; that the 
first postoral ganglion pair is not in all cases that of the 
mandibles ; aud finally, that the nerves of the two first pairs 
of appendages are, in certain thoroughly typical Crustacea, 
given off from the lateral cords at a point far removed from 
the archi-cerebrum. 
Whether the ganglion (G1) has any relation to the nerves 
of the first and second antennz might possibly be determined 
by a microscopical examination of the roots of those nerves. 
In the course of the foregoing pages I have alluded to 
some points of resemblance between Apus and Limulus, 
the most important being the jaw-processes at the base of 
all the ambulatory limbs, and the presence of a pure archi- 
cerebrum in both genera. 
I should wish, however, to guard against the inference 
that I consider any close affinity to obtain between Apus 
and Limulus. Apus appears to me to be an archaic Crus- 
tacean, and Limulus an archaic Arachnidan (not merely 
therefore be very grateful to any naturalist who would send to me by post 
perfectly fresh living examples of Apus. 
