128 DR. E. KLEIN. 



cells the nucleus as containing a nucleolus, from which fibrils pass 

 in a radial direction outwards into the surrounding cell-substance, 

 where they form a network. That the small regular dots present 

 in the intranuclear network are merely optical sections of fibrils, as 

 also maintained by Eimer,^ I have not the least doubt of, although 

 Balfour, in his paper on the structure and development of vertebrate 

 ovary,~ does not accept this interpretation for the bright dots in the 

 reticulum of the germinal vesicle. Looking at some of his 

 figures, e.g. figs. 3, 16, 18, I recognise the very identical ap- 

 pearances, i.e. uniform dots in the nodes of the network, and I 

 should think a high power, very good light and careful focussing 

 would show that my interpretation is the correct one. That 

 the larger particles occasionally to be noticed in the network are 

 the remains of the substance out of which the network is de- 

 veloped, as Balfour maintains in the case of the germinal 

 vesicle, I have no doubt is the true explanation also of the 

 natural local accumulations which were noticed by me in some 

 nuclei of the cells of newt, and which may be seen also in some 

 of those of the intestinal epithelium. So that we both agree 

 with Schwalbe,^ who, as I have mentioned in my first paper, 

 regards the nucleolus and other large particles in the nucleus 

 as of transitory value in the developmental history of this organ. 

 Prom my own experience I am led to conclude that in the 

 development of the cell-nucleus a stage is reached — in some pro- 

 bably sooner than in others — in which the intranuclear network 

 may be regarded as fully formed, being uniformly constituted 

 and without containing any more of those large particles. Such 

 nuclei may be met with in large numbers in the epithelial cells 

 of stomach of newt, in the endothelial and unstriped muscle cells 

 of mesentery of newt, and also in the epithelial cells of intestine 

 of mammals. In all these organs most nuclei contain a uniform 

 reticulum without any large particles. The small uniform dots 

 present in them, I repeat, are only optical sections of fibrils. 



1 should invite my friend Mr. Balfour to consider the following simple 

 proposition : the intranuclear as well as the intracellular network having, of 

 course, three dimensions, includes fibrils that lie in the two dimensions of 

 the plan of the field of the microscope, as well as fibrils placed vertically to it. 

 The former appear, of course, as fibrils ; but, I should like to ask, as 

 what do the latter appear, i. e. those situated vertically ? Clearly as dots, 

 because they are seen endwise ; and for obvious reasons most of them lie 

 in the nodes of the network. 



The above stage of ripeness, if I may be allowed to call it so, 



^ ' Archiv. f mikroskop. Anatomic,' Band, xiv, p. 103. 



2 This Journal, vol. xviii (New Ser.), October, 1878, p. 437. 



^ " Bemerk. iiber d. Kenn. d. Ganglienzellen," ' Jenaisch. Zeitsclir.,' 

 Band x, p. 25. 



