36 Journal of Comparative Neurology and Psychology. 



ognized method being the extrusion of very small granules 

 (See page 33). 



Judging from the staining reaction of the accessory nucleoli 

 which contain both phosphorus and iron, they are composed 

 of the same substance as the Nissl granules and therefore it 

 may be safely concluded that the disintegrated substance was 

 utilized for the formation of the Nissl granules. This observa- 

 tion agrees with that of Rohde, but with his further statement 

 that some of the accessory nucleoli become the neuroglia 

 nuclei, I cannot agree. So far as my observations on the nerve 

 cells of the white rat go, there is no indication that the accessory 

 nucleoli form the nuclei of the neuroglia cells. The migration 

 of the accessory nucleoli was found only in the cells at the early 

 stage of intrauterine life here examined, and at more advanced 

 stages I was unable to observe this phenomenon, although a num- 

 ber of later developmental stages were studied. From this 

 fact, we may conclude that extrusion of the nuclear substance 

 into the cytoplasm occurs only in the very early stages of the 

 developing nerve cells. 



Significaficc of the psendopodia-like processes of the nucleus. — 

 The observations of the previous investigators (Holmgren, 

 Rohde and Scott), as well as those presented in this paper, 

 furnish good evidence for believing that Nissl granules originate 

 in at least two ways ; namely (i) by the extrusion of small 

 granules; (2) by the extrusion of accessory nucleoli. If all 

 the materials which appear in the Nissl gran\iles of the mature 

 nerve cell are derived from the chromatin of the nucleus, then 

 it is plain, since the nucleus at no time contains as much sub- 

 stance as is presented by the Nissi. granules at maturity, that 

 the chromatin of the nucleus must be continually built up by 

 the niaterial supplied to it from the cytoplasm. So far as I am 

 aware no investigator except Holmgren ('99) has attempted 

 to explain this phenomenon. Holmgren found in the nerve 

 cells of Lophius piscatorius that the Nissl granules are hung along 

 the astral rays which run through the nuclear membrane and 

 according to him this indicates the return of the Nissl granules to 

 the nucleus by way of the astral rays. Thus, according to him. 



