412 DR. E. KLEIN. 



nuous and rapid shedding of the superficial layer of the cells 

 of the epidermis, it naturally follows that a corresponding 

 continuous and rapid new formation of epithelial cells takes 

 place, and accordingly I investigated the epidermis in sections, 

 in order to find, as I expected to find, signs of division of 

 cells and their nuclei. The adult newt being an animal 

 easily procured during the greater part of the year, and its ele- 

 ments being considerably larger than most other vertebrates, 

 easily accessible, would, therefore, be a good object for 

 studying those exceedingly interesting phenomena accom- 

 panying the division of nuclei, as first described by 

 Strasburger, Biitschli, Mayzel, Eberth, Hertwig, Auerbach, 

 Balfour, and especially very recently in the beautiful obser- 

 vations of Fleniming, Schleicher, and Peremeschko. My 

 expectations were fully realised by the examination of the 

 epidermis of the adult newt, and I will here describe the 

 appearances presented by the dividing nuclei of the epider- 

 mis very briefly, since my observations in many respects fully 

 coincide with those of Flemming and Peremeschko, observed 

 by the former in Salamandra rnaculosa and its embryo, by 

 the latter in the embryo of Triton cristahfs. Following the 

 plan of Flemming (' Avchiv f. mikro Anat.,' Bnd. xvi, p. 

 363), I hardened my object in picric acid or chromic acid 

 and stained it afterwards in hsematoxylhi, and I found it 

 very good for the demonstration of the different forms of 

 dividing nuclei. The picric acid I used is a mixture of two 

 or three parts of a saturated solution and one part of water, 

 the chromic acid is a ^ per cent, solution. Bits of tail 

 — about J or ^ inch long — are placed in either of these 

 fluids and kept there for seven to ten days, they are 

 then placed for a short time (j or 4^ hour) in spirit, em- 

 bedded and used for cutting fine vertical sections. These 

 are thoroughly washed in Avater, stained in very dilute 

 hsematoxylin and then prepared in the ordinary way for 

 mounting and preserving in solution of Canada balsam. 

 The sections prepared in picric acid are preferable to those 

 in chromic acid, although the latter have many good points 

 about them. 



The phenomena of division of nuclei to be observed in 

 these specimens are confirmatory of the statements made 

 by Flemming in his very exhaustive article, in which he 

 minutely describes the different changes the intranuclear 

 network undergoes during division, as observed by him in 

 the living state and after reagents. In the same paper 

 Flemming gives an exhaustive and critical review of the 

 observations and assertions on the same subject by his pre- 



