Houser, Zhe Neurones of a Selachian. 131 
reticulum of Gore (1900). We find the internal part of the 
cytoplasm exhibiting deeply stained, massive bodies, branching, 
and anastomosing with each other through more slender connec- 
tions. The several individual masses are disposed in such a 
way as to give the appearance of enclosing the nucleus as with 
an open network. The bodies fade away as they enter the 
dendrites, and there is no appearance of their having communi- 
cation with the exterior such as has been described by Hoim- 
GREN (’99a, ’99b). Fig. 57 represents the appearance of this 
series of structures. 
It is doubtless necessary to await further researches in 
many distantly related fields before we attempt to pass final 
judgment as to the significance of the perinuclear reticulum, 
but the hypothesis noted by Gorer (1900) is one which cer- 
tainly deserves our consideration. The appearance presented 
by the network may be caused, not by solid bodies at all, but 
by a series of communicating canaliculi filled with a fluid which 
is deeply colored by certain stains. Such a reticular canal- 
system would probably take no part in the irritable life of the 
cell as such, but would function ona lower plane of purely 
vegetative character. | 
The neurones of the roof-nucleus come into intimate rela- 
tions with the nerve-fibres of the stratum medullare profundum. 
The dorsal decussation between the opposite halves of the stra- 
tum carries a strong bundle of fibres across the median plane 
immediately above this group of neurones (Fig. 55, dc. s. m. 
p.). There are to be found here numerous instances of nerve- 
fibres emerging from the general bundle and terminating in 
arborizations near the bodies of the nerve-cells. Fig. 57, a7, 
represents two-such arborizations near the same cell. The char- 
acter of the termination is exceedingly interesting. The axones 
are found to present a reticulo-vesicular structure throughout 
- their whole length, the protoplasm apparently consisting of 
vesicles of several degrees of size united by a reticulum. Now 
as the axone approaches its termination, the reticulation be- 
comes more pronounced, and the final arborization is seen to 
be essentially an expansion of the same thing. The ending is 
