212 Journal of Comparative Neurology. 



studies in the anatomy of the Torpedo brain similar double cells 

 have again come under observation and it is the significance 

 of these cells in the solution of the problems of brain 

 growth and especially the histogenetic processes which are in- 

 volved to which I wish to invite special attention. I have been 

 able to determine that these double cells in the Torpedo brain 

 may by their complete separation from one another become the 

 ordinary ganglion cells of the brain. In the figures which I 

 shall publish soon, some of the cells are reproduced with great 

 care. All the figures are camera drawings, and are taken from 

 sections of the brain of an adult Torpedo occidentalism the sec- 

 tions being stained by Weigert's method. No single case of 

 the karyokinetic process (in the nucleus) has been found in my 

 preparations but the other relations and conditions of the cells 

 leave no doubt that here in the Torpedo brain functional cells 

 actually divide in the manner so well known for ordinary tissue 

 cells. The stages of cell division which occur in the electric 

 lobes are as follows : 



(i). Large motor cells, not to be distinguished from the 

 ordinary functional cells except by the size of the nucleus and 

 cell body. 



(2). Cells of the same size as (i) but with two nuclear 

 bodies. Both may be close together in the centre of the cell 

 or widely separated and lying near the periphery of the cell. 



(3). Cells showing an evident constriction of the proto- 

 plasmic body between the nuclei as though about to divide. 



(4). Double cells with short connecting bars which, are 

 usually large and band-shaped. 



(5). Double cells in which the connecting bar is drawn 

 out into a thin filament, tapering conically from either cell body 

 towards the other. 



(6). Since each nerve cell of the brain and ganglia has a 

 peri-lymphatic capsule surrounding it, when the cell body is cut 

 into two the peri-lymphatic space is not at once doubled but 

 the two cells still lie in a common cavity. Because of this it is 

 possible to trace the genetic relation of these electro-motor cells 

 even after they have completely separated by the breaking of 



