THE CELL DOCTRINE. 125 



minute bright spots, which are shown by careful 

 focussing to be fibrils of the network seen in optical 

 transverse section or at the points of anastomosis. 

 In some nuclei, according to Klein, the more irregu- 

 larly shaped dots are due to a thickening of fibrils 

 from place to place, although Flamming attributes 

 them altogether to the former cause^ (transverse sec- 

 tions of fibrils). Whence it is clear, the more shrunk 

 the intranuclear uetwoz'k, or the more twisted and 

 convoluted the fibrils, the more does the nucleus 

 present the appearance of being granular. 



The nucleolus receiv^e an entirely peculiar expla- 

 nation at the hands of Klein, in which he seems to be 

 sustained by the observations of Van Beneden, 0. ' 

 Hertwig, Flemming himself, Auerbach, Eimer, and 

 especially of Strasj^burger, Schwalbe, and Langhans. 

 With regard to it Klein first says with undoubted 

 truth : " I^fow, to every experienced student of his- 

 tology, 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." Second, that after 

 a very prolonged examination he has arrived at the 

 conclusion that these large particles (nucleoli) are 

 due to one of two things : in some instances they are 

 distinctly thickenings of the network, in others they 

 appear to be merely due to the shrivelling up and 

 intimate fusion of a part of the network. The in- 

 constancy as regards size, shape, and number of the 

 so-called nucleoli seem to him to point very strongly 

 in the above_ direction. 



The assertions which have been made as regards 

 11* 



