Houser, The Neurones of a Selachian, — 147 
mass, or general striatum, will be considered after that of the 
epistriatum. 
a. Epistriatum.—tThe epistriatum isa group of neurones 
lying ventral and lateral to the lateral ventricle (Fig. 31, est). 
It comprises something like the inner fifth of the entire thick- 
ness of the striatum. While not so sharply delimited from the 
outer levels as EDINGER ('96) has described for the reptilian 
brain, the epistriatum of Mustelus is readily distinguished from 
the general striatum by the smaller size and more closely 
crowded disposition of its neurones. The neurones are not 
arranged in any definite order; they are of the Golgi II type, 
sending their axones ventro-laterally into the striatum; refer 
tome... °3 2. 
The cell-body of such a neurone ranges from triangular to 
polygonal in outline. There are three or four dendrites of only 
moderate length. These seldom branch except near their bases. 
They bear a very few gemmules and irregular knobs. The den- 
drites may extend indifferently in all directions, or they may lie 
tangential to the limitans interna. 
The axone may arise from the cell-body, but in many in- 
stances observed it emerges from the thick base of a dendrite. 
It passes into the region of the general striatum, bearing short 
collateral branches along its whole length, and ultimately divid- 
ing into a widely spreading arborization between the neurones 
of the outer levels. Fig. 33 shows the external features of one 
of these neurones. 
The internal structure of the neurone is shown in Fig. 65. 
The nucleus is seen to fill the greater part of the cell-body. 
It presents an oval form, and has chromatin disposed in a few 
relatively large masses, each consisting of a central clot with 
radiating streamers. There isa single nucleolus. The cyto- 
plasm lies chiefly in the bases of the larger dendrites. Its 
tigroid-bodies are small in size, few in number, and irregular 
both in form and distribution. Judging from the structure pre- 
sented by this neurone, it is not characterized by a high degree 
of metabolic activity. 
The epistriatum is one of the nuclei for the termination of 
