TuRNER, Mushroom Bodtes of the Crayfish. 327 
6. From the posterior swelling fibers pass to the outer 
and inner nidus of the lateral swellings, to the optic nerves and 
to the antenne. 
7. Unlike Bercer, he does not think that any fibers 
arise from the anterior nidus. 
8. Did not succeed in tracing any tracts into the collar. 
G. Rerztus (’90) gives an exhaustive historical resumé and 
demonstrates beyond a doubt the value of methylen-blue as a 
stain for nerve fibrils. 
JuLes Ricwarp (’g1) after a careful study of the nervous 
systems of Diaptomus and Cyclops, arrived at the following 
conclusions : 
1. The nervous system resembles that of marine cope- 
pods of the same family. 
2. The whole central nervous system is enveloped ina 
delicate membrane. 
3. Certain parts of the brain contain unipolar but no 
multipolar cells. He also finds bipolar cells. 
He does not discuss either the central body or the mush- 
room bodies. . 
Paut Samassa (’91) studied Szda crystallina, Daphina sima, 
Mutter, Bythrotrephes longimanus, Leypic and Leptodora hya- 
fina, LittyEBoRG. All of his methylen-blue preparations were 
a failure, but osmic-acid preparations gave good results. 
1. _ Among all the Cladocera the central nervous system 
consists of the following four parts; the optic ganglia, the 
brain, the oesophageal commissures and the ventral chain. The 
brain and optic ganglion lie in front of the oesophagus. In 
Daphina the optic bodies are united to the brain by two stalks, 
but in Szda they are fused with the brain. In Leptodora the 
brain and optic ganglion lie immediately beneath the eye. 
2. In Szda the ventral_chain consists of two longitudinal 
strands which are united by nine transverse commissures ; but 
in Leptodora the ventral chain is fused into one mass. 
3. The brain of Szda is composed of two pear-shaped 
masses, the ‘punktsubstance’ of which has the shape of the letter 
H, resembling in this respect the grey substance of the myelon. 
