Genetic Relation of Neurofibrillae to Chromatin. 83 



fibrillation. In the drawing however, on the other side of the plate, 

 the individual chromatin particles and chromoflbrillae have been 

 sketched from the camera lucida, therefore it is possible to vouch 

 for their accuracy. 



Fig. 7 is a chromofibrillar bundle originating from a nucleus 

 in the grey matter of the spinal cord and extending far into the 

 white, where its further course down the spinal cord is to be 

 followed in the adjacent sections. This serves as an illustration of 

 the length to be attained by such fibrillae as well as the exact 

 mutual relation. The portion of the nucleus at the left consists 

 primarily of parallel fibrillae, with only a localized portion of 

 granular chromatin, which appears to be in the act of constricting 

 oif into a mucleus. This structure however the photograph fails 

 absolutely to distinguish because of the fact that this particular 

 region is far out of focus. In the distal portion the chromofibrillae 

 are no longer bounded by a nuclear membrane. In particular areas 

 they are quite widely separated from one another — a condition of 

 relative independence, yet at the same time retaining the general 

 form of a bundle. Further on, however, in the adjacent sections, 

 they are seen to soon resume the form of a relatively compact 

 bundle. 



The Purkinje cell in Fig. 8, from the cerebellum of S. maculosa, 

 is selected merely to represent a stage of difterentiation in advance 

 of Fig. 4. The last traces of visible connection between the neuro- 

 fibrillae and nucleus have disappeared. The sole remnant of guilt 

 betrayed by the nucleus is the maintenance of a distinct polarity — 

 an enormous "chunk" of plastic chromatin still protruding in the 

 direction of the finished structures. 



The large nucleus in Fig. 9 is of a multipolar ganglion cell 

 from the central grey matter of the spinal cord. It is to be con- 

 trasted with Fig. 1. It is a quite logical explanation of the striking 

 difference in chromatin content to consider that the neurites of the 

 former exceed in number those of the latter by at least eight. It 

 is a proposition quite similar to that of pouring rocks out of a sack, 

 if such an absurd comparison were permissible. The rocks decrease 

 in number in the course of time just as the chromatin has decreased 

 in quantity. 



6* 



