OBSERVATIONS ON STRUCTURE OF CELLS AND NUCLEI. d.^O 



fractive, large dol, called nucleolus ; the best known examples 

 are the nucleus of ganlion-cells and the germinal vesicle 

 or nucleus of ovum. Many nuclei contain more than one 

 nucleolus; which are described as of the same, or as is more 

 commonly the case, of different sizes. Now, to every ex- 

 jierienced student of histology it must have become apparent 

 that if there is one thing unsatisfactory, unreliable, puzzling 

 and inconstant about the nucleus of vast numbers of cells, 

 it is this very nucleolus. Flemniing (1. c, p. 702) maintains 

 that in the case of the nuclei of the bladder of Salamandra 

 'nucleoli' are present and may be demonstrated by 

 anilin staining. But looking at his drawings {Hgs. 9,a, b, 

 c, and d) I fail to see the justice of this conclusion. What 

 is here shown in the nucleus are 7iii>nhcrs (a dozen and 

 more) of more deeply stained, irregularly-shaped masses 

 placed in the fibrils of the network. 



Thus, for instance, in d of his fig. 9, Flemming shows us 

 two nuclei of unstriped muscle fibres, each of which contains 

 in the network of fibrils, only faintly seen, an uncountable 

 number of irregularly shaped particles. Why he should 

 regard all these particles as definite anatomical structures 

 identical Avith the spherical bright large spot, which is 

 generally characterised as nucleolus, I fail to comprehend. 

 Arguing against Schwalbe, Flemming (1. c. p. 7 lo) thinks that 

 " the nucleoli at all events do not repiesent merely local 

 accumulations of the network, but are or may be in many 

 cases something different." 



In the nuclei of the cells of the stomach of newt, prepared 

 in the above manner, I do not find in the great majority of 

 instances any signs of what is usually accepted as a nucleolus ; 

 only in a few instances I saw one or two particles (larger than 

 the ordinary bright dots above explained) which correspond 

 to Flemming's ' nucleoli.' Now, I have after a very pro- 

 longed examination arrived at the conclusion that these 

 large particles are due to one of two things ; in some instances 

 they are distinctly thickenings of the network, in others 

 they appear to bo merely due to the shrivelling up and inti- 

 mate fusion of a part of the network. And this seems to 

 me to be borne out also by the examination of nuclei of 

 the stomach or palate of newt in the fresh condition, I 

 have seen distinctly that when the neucleoli are present — the 

 instances are fewer than is generally supposed — they are accu- 

 mulations of the fibrils of the network. The inconstancy as 

 regards size, shape and number of the so-called nucleoli 

 seems to me to point very strongly in the above direction, 

 viz. that they are due merely to a local thickening (natural 



