328 JouRNAL OF COMPARATIVE NEUROLOGY. 
4. Acentral body is found in the brains of Szda, Daph- . 
nia, Bythrotrepes and Leptodora, but in no case did the author 
observe any fibers entering or leaving the body. 
5. In Szda the nerves to the second antenna arise from 
ganglia in the collar, which ganglia are connected by a com- 
missure. 
6. In Szda, the oesophageal commissures terminate in 
the mandibular ganglion. 
7. The maxillary ganglion is located in the collar, but has 
no commissure. 
6. In Szda there are six pairs of feet ganglia and one pair 
of dorsal ganglia [Stenerborsten-ganghen] each having a com- 
missure. 
The paper also contains a résumé of the work done on the 
nervous system of the Cladocera. 
H. VIALLANEs’ (’93) contribution is of such value that it is 
thought wise to give a résumé of his conclusions concerning 
not only the Crustacea but all the Arthropoda. 
General Remarks on the Organization of the Nervous System 
of the Articulates. There are two types of nerve cells; gan- 
glionic and chromatic. The chromatic have very little proto- 
plasm. The nerves are formed of axis cylinders which react 
chemically in the same manner as nerve cells. 
The nervous centers are composed of neuroglia, axis-cylin- 
ders and nerve cells. There are three types of axis-cylinders ; 
centrifugal, centripetal and intrinsic. The centrifugal fibers, 
which are of about equal diameter throughout, arise from the 
large ganglion cells and constitute the motor fibers of the 
nerves. Along their course they give off lateral ramifying 
branches. The centripetal fibers are sensory. On entering the 
nerve center they ramify into finer and finer branches, but are 
not attached to the nerve cells. The intrinsic axis cylinders 
are ramifying fibers which arise from small cells which are situ- 
ated in the ganglionic centers. 
The nervous system begins as two longitudinal thickenings 
of the ectoderm which occur on each side of the meson. These 
thickenings fuse in front of the mouth to form the brain and 
