MUSEUM OF COMPARATIVE ZOOLOGY. 271 



sis for the fibrils, or their optical cross-sections ; moreover, some fibrils possess 

 irregular thickenings. Nuclei examined in a perfectly fresh condition, with 

 favorable light and powerful objectives (e. g. Hartnack, Imm. 10), show distinct- 

 ly, although faintly, part of the intranuclear network. Klein disagrees with 

 Flemmiiig when the latter finds ground for believing in the existence of nucle- 

 oli fundamentally difi'ering from the granules which are referable to thicken- 

 ings in the network. - At best, the so-called nucleoli are due to a shrivelling 

 and intimate fusion of a part of the network, and are only transitory ap- 

 pearances. In the fresh condition it is demonstrable that the nucleoli are 

 " accumulations of the fibrils of the network." 



An mtrsicellular network is also conspicuous in most of the cells studied. In 

 epithelial cells that have retained their cilia, the latter are seen to pass into the 

 cell substance and identify themselves with the intracellular network, the fibrils 

 of which in turn are in direct connection with the intranuclear network. 



" In all muscle fibres the intranuclear fibrils may be traced to emerge as a 

 bundle from the pole of the nucleus, and to become identified with the bundle 

 of fibrils representing the core of the muscle-fibre itself." The nucleus pos- 

 sesses a small circular hole at each pole through which these fibrils emerge. 

 Klein says that, after giving the point the greatest attention, he has been unable 

 to find any evidence of a connection between the axis cylinder of nerve fibres 

 and the intranuclear network ; on the contrary, he is able in most instances to 

 follow the axis cylinder along one side of the nucleus beyond the latter. This 

 he thinks is the normal relation of the axis cylinder to the intranuclear 

 network. 



Flemming ('78^) publishes in a preliminary paper some of the results of 

 studies conducted on the simple plan of choosing for examination such objects 

 as permit a comparison of the living cells with stained preparations of the 

 same. Numerous tissues, especially of the salamander, are made the objects 

 of study, and the phenomena carefully reproduced in numerous figures. 



The first of the two main divisions of the paper treats of the structure of 

 the quiescent nucleus ; the second, of cell division in growing and in inflamed 

 tissues. The quiescent nucleus examined in the living condition exhibits a 

 network which, however, varies in difi'erent cases, and is not so regular as often 

 portrayed. The various appearances produced by the use of reagents — which 

 p-ary in the reliability of the results produced — undoubtedly find their expla- 

 nation in the existence of a corresponding structural differentiation in the 

 living nucleus, but how far the intranuclear structures which appear after 

 treatment with acids are identical with the living condition, cannot be so read- 

 ily determined. Even with the best preservative reagents there is more or less 

 iistortion. The fine granulation of chromic acid preparations is held to be 

 iue to coagulation, as are possibly some of the smaller fibres of the network^ 

 3ut certainly not all. The eff'ect of the chromates is especially imtrustworthy. 

 I The results touching the nature of the quiescent nucleus are summarized 

 )y the author himself much as in a previous paper (Flemming, '78). The 

 [uiescent nucleus consists of, — 



