402 GEOLOGICAL SURVEY OF THE TERRITORIES. 
poor success attended our efforts. The brain lies, as seen in fig. 2, in 
the midst of the liver, and in the process of cutting through the head 
the brain slips aside from or crumbles before the edge of the razor. Of 
course the only proper way is to remove the brain from the living animal 
and properly prepare it for the microtome; but this is next to impossible 
owing to its small size. Indeed, the difficulties in the way of making a 
good dissection of the brain of these creatures, particularly Apus, are 
very great. After working for some time at the brain of well-preserved 
Apus lucasanus, we were able to satisfy ourself that the drawings and 
descriptions of Zaddach in his classical work on Apus cancriformis are 
correct, although his drawing of the entire ventral chain (his Tab. III, 
fig. 1) might be improved; his representations of the brain are undoubt- 
edly correct enough for all practical purposes, and we have copied in 
Plate XX XII three of his excellent figures. The figure of the entire 
nervous system of Apus lucasanus (Plate XXXII, fig. 1) was drawn by 
Mr. Kingsley, and adopted with some important corrections in the posi- 
tion and form of the brain. The sketch is necessarily in part diagram- 
matic, and no nerves to the appendages are represented. AS seen in 
the copies of Zaddach’s figures the brain is small, situated right under 
the compound eyes, and it innervates only the simple eye or ocellus 
and the compound eyes. The nerves to the two pairs of antenne, fig. 5 
(ant', ant’), arise from the commissures, and not from the supracesoph- 
ageal ganglion. The rest of the nervous cord is ladder-like. 
In the Branchipodide the nervous system shares with the other sys- 
tems of organs in a general advance to a higher plane of organization. 
According to Claus excellent figures of the brain, especially of the very 
young Branchipus stagnalis, the nerves to the first and second antennze 
arise from groups of ganglion-cells situated on the outside of the com- 
missures, the ocellus and two stalked eyes being innervated from the 
brain as in all other Phyllopods, and it will probably be found that in 
the early stages the commissures are provided with ganglionic enlarge- 
ments from which the appendages of the head are innervated; thus there 
may be a slight resemblance in this respect to the ganglionic esophageal 
ring of Limulus. 
We have, then, in the subesophageal ganglion of all the Phyllopods 
a simple, small ganglion, no more differentiated than those forming a 
part of the ventral cord. Plate X XIII, fig. 1, gives a vertical view of 
the brain of the adult Artemia, which is nearly continuous with the 
optic ganglion. On Plate XXXIII, fig. 8, is represented a section of 
the small brain of Branchipus vernalis. It is very simple in structure, 
the ganglion cells small, scattered, and indistinct. Fig. 8a shows the 
ganglion cells enlarged. No fibers appear, though more careful ob- 
servations than I was able to make are needed before we can have a 
complete knowledge of the brain of the supracesophageal ganglion in 
the Phyllopods. 
For the structure of the abdominal portion of the nervous cord the 
reader is referred to Leydig’s account and his figure in Tafeln zur Verg. 
Anatomie, Taf. V, fig. 5. 
It is apparent, however, that in the Phyllopoda the brain is a very 
simple affair, and not much higher in complication of structure than the 
brain of worms, and when we compare it with the brain of the Decapods, 
or at least that of the crayfish and lobster, these alone having been 
studied, we are comparing two very different organs. The brain of the 
Decapoda is an aggregate of at least two pairs of ganglia besides the 
primitive pair innervating the eyes. The extreme degree of cephaliza- 
tion, by which the head becomes more compact and homogeneous, has 
had its resultant effect upon the primitive brain and the ganglia behind 
