326 JOURNAL OF COMPARATIVE NEUROLOGY. 
7. The central ganglia are composed of nerve fibers and 
the prolongations of nerve cells. 
8. The nerves of the stomatogastric system have the 
same structure as those of the ventral chain. 
The author does not give a detailed description of the 
supra-oesophageal ganglion. 
K. RicHARD KRIEGER (’88) truly remarks that EHRENBERG, 
VALENTIN, HerMHOLTz, REMAK, HANNOVER, WILL, HAECKEL 
and other early observers, studied the histological elements only 
and ignored their relationships. He gives an instructive topo- 
graphical drawing of the brain. Ignoring those portions which 
have no direct bearing upon the subject under discussion, the 
paper contains the following conclusions: 
1. The brain of the crayfish is composed of the follow- 
ing four portions: An anterior swelling, a posterior swelling 
and two lateral swellings. These names explain the location of 
the parts. The anterior swelling consists of three portions, 
a median anterior nidus of cells, below which come, in the order 
named, the paired anterior and posterior bundles of ‘punktsub- 
stance’ of the anterior swelling. The lateral swelling also con- 
tains an anterior and posterior bundle of ‘punktsubstance.’ On 
both the inner (mesal) and outer (lateral) sides of the anterior 
bundle of ‘punktsubstance’ of each lateral swelling lies a nidus 
of cells. The posterior swelling likewise contains a pair of 
anterior and a pair of posterior bundles of ‘punktsubstance.’ Be- 
tween the anterior bundles lies a median nidus of cells; and 
the lateral portion of each posterior bundle is partly covered 
by a nidus of cells. 
2. The ganglion cells have no membranes. 
3. Two prominent optic tracts, coming from what DietL 
and BERGER consider the homologue of the mushroom bodies, 
form a chiasm where all the fibers decussate. 
4. There isa prominent tract which passes from each 
lateral swelling to the optic nerve of the same side. 
5. From the anterior swelling fibers pass to the inner 
nidus of the lateral swelling, the outer nidus of the same and 
to the antennules. 
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