356 H. M. BERNAK'D. 



passage of chromatin upon them. I refer to the fibrils 

 running- in or upon the walls of the rods, and also to the 

 nerve-fibrils in or on the membranes of the supporting frame- 

 work of the nerve-strand. 



These are the leading facts with regard to the morphology 

 and physiology of the protomitomic system of the retina, so 

 far as they have been revealed by these researches. Not 

 many of them are new. As we have already noted, the 

 " prickles " joining the nuclei to the cytoplasm were described 

 as universal phenomena by Heitzmann, and have been fre- 

 quently figured since. The existence of intercellular bridges 

 between the cytoplasmic masses Avhich usually surround the 

 nuclei have been recorded sufficiently often to justify the 

 assumption that they are fundamental factors in multicellular 

 organisms. The existence of a fibrillar substance under- 

 lying the cytoplasm, and even running in the walls of the 

 alveoles in those cases in which the cytoplasm appears to be 

 a foam structure, completes the series. If we put these 

 together, as Professor Macfarlane has tentatively done for 

 plant tissues, and as we are now completely justifietl in doing, 

 we arrive at the protomitomic system which the retina has just 

 clearly and directly revealed to us, owing to the fact that so 

 many C)f its nuclei are unobscured by any granular cytoplasm. 

 Further, that the nerves were bundles of primitive nerve-fibrils 

 has long been known. That these primitive fibrils occasionally 

 run into the intra-nuclear reticulum has been seen by several 

 observers, but, owing to the element of chance, first in finding 

 the filaments preserved, and then, if preserved, in the right 

 physiological condition to be rendered visible under ordinary 

 powers of the microscope, confirmation has not been forth- 

 coming. The striation of the rods was well known, :nul its 

 connection with the primitive nerve-fibrils was suggested by 

 Max tSchultze. The expulsion of nucleoplasm from the nuclei 

 has been described, and the contractibility of the protomitomic 

 filaments has been maintained, in order to account ft)r some of 

 the phenomena of mitotic cell division, and for the movements 

 of leucocytes. And, lastly, the growth of the primitive nerve- 



