22O MICHAEL F. GUVER. 



and counter-stained with Congo red or acid fuchsin, although 

 Delafield's haematoxylin was used with some. 



An abundance of cell divisions were found to have been in 

 progress at the time of death. In a given field of the microscope, 

 in a favorable region, it was not unusual to observe as high as 

 six or seven cells in various phases of division. As many as five 

 or six of such areas might exist in a single section, although it 

 was more usual to find only one or two. The material was very 

 uneven in that slides would be found in which section after sec- 

 tion showed division stages, while in others divisions were scarce. 

 These facts indicate that there were proliferating and resting 

 zones in the testis. The stages found in most abundance were 

 the metaphases and late prophases of the primary spermatocytes. 

 It was a comparatively simple matter to find spindles on which 

 the ordinary chromosomes were in metaphase with the two 

 accessories, closely associated, well removed toward, or at, one 

 pole (Figs. 6, 7, 8 and 9). 



In the literature of the subject much confusion prevails re- 

 garding the number of chromosomes characteristic of man. 

 There is wide disagreement in the counts of different observers 

 and there seems to have been a great dearth of material showing 

 division stages. Most of the enumerations are based on obser- 

 vations of from two to eighteen cells and these often in ques- 

 tionable stages of preservation. The great difficulty apparently 

 has been to secure material which was sufficiently fresh or which 

 was not diseased tissue that is notoriously irregular as regards 

 karyokinetic phenomena. 



As early as 1881 Flemming discussed mitosis in the case of 

 man illustrating it with some six figures (Taf. 3, Figs. 11-16) 

 of which Fig. 16 is from leucocytes of leucemic blood, the others, 

 from the corneal epithelium of two different subjects from each 

 of whom an eye had been removed because of affection of the 

 bulbus. Although at this time he made no definite record of 

 the number of chromosomes, his drawings show them to be 

 considerably in excess of sixteen, the number later announced 

 by Bardeleben ('92). 



Writing several years later, however, in response to the 1892 

 paper of Bardeleben, Flemming ('97), from a reexamination ot 



