DIRECT OR AMI TO TIC DIVISION 



multiplication. It is frequent in pathological growths and in cells 

 such as those of the vertebrate decidua, of the embryonic envelopes 

 of insects, or the yolk-nuclei (periblast, etc.), which are on the ivay 

 toward degeneration. In many cases, moreover, direct nuclear divi- 

 sion is not followed by fission of the cell-body, so that multinuclear 

 cells and polymorphic nuclei are thus often formed. These and 

 many similar facts led Flemming in 1891 to express the opinion that 

 so far as the higher plants and animals are concerned amitosis is "a 

 process which does not lead to a new production and multiplication 

 of cells, but wherever it occurs represents either a degeneration or an 

 aberration, or perhaps in many cases (as in the formation of multi- 

 nucleated cells by fragmentation) is tributary to metabolism through 

 the increase of nuclear surface." * In this direction Flemming 

 sought an explanation of the fact that leucocytes may divide either 

 mitotically or amitotically (/. Peremeschko, Lowit, Arnold, Flemming). 

 In the normal lymph-glands, where new leucocytes are continually 

 regenerated, mitosis is the prevalent mode. Elsewhere (wandering- 

 cells) both processes occur. " Like the cells of other tissues the 

 leucocytes find their normal physiological origin (Neubildung) in 

 mitosis ; only those so produced have the power to live on and repro- 

 duce their kind through the same process." 1 Those that divide ami- 

 totically are on the road to ruin. Amitosis in the higher forms is 

 thus conceived as a purely secondary process, not a survival of a 

 primitive process of direct division from the Protozoa, as Strasburger 

 ('82) and Waldeyer ('88) had conceived it. 



This hypothesis has been carried still further by Ziegler and Vom 

 Rath ('91). In a paper on the origin of the blood in fishes, Ziegler 

 ('87) showed that the periblast-nuclei in the egg of fishes divide ami- 

 totically, and he was thus led like Flemming to the view that amitosis 

 is connected with a high specialization of the cell and may be a fore- 

 runner of degeneration. In a second paper ('91), published shortly 

 after Flemming's, he points out the fact that amitotically dividing 

 nuclei are usually of large size and that the cells are in many cases 

 distinguished by a specially intense secretory or assimilative activity. 

 Thus, Riige ('90) showed that the absorption of degenerate eggs in 

 the Amphibia is effected by means of leucocytes which creep into the 

 egg-substance. The nuclei of these cells become enlarged, divide ami- 

 totically, and then frequently degenerate. Other observers ( Korschelt, 

 Carnoy) have noted the large size and amitotic division of the nuclei 

 in the ovarian follicle-cells and nutritive cells surrounding the ovum in 

 insects and Crustacea. Chun found in the entodermic cells of the 

 radial canals of siphonophores huge cells filled with nests of nuclei 

 amitotically produced, and suggested ('90) that the multiplication of 



1 '91, 2, p. 291. 



