606 



Patterson (1908) has made a careful study of cell division during 

 gastrulation in the pigeon. He reports and illustrates mitosis mainly 

 in the slowly, and amitosis in the rapidly, growing parts of the blasto- 

 derm, both in the entoderm and the mesoderm. He shows that mi- 

 tosis may follow amitosis and vice versa, and concludes that amitosis 

 is "the result of special physiological conditions" involving factors 

 that stimulate rapid growth, p. 125. 



WiEMAN (1910) reports amitosis in the germ cells of both sexes 

 of the potato beetle, Leptinotarsa signaticollis. He believes the 

 condition to be due to "a periodic fluctuation in the nutritive supply 

 of the germ cells, brought about b}^ a stimulus to a rapid cell division 

 which causes a temporary derangement in the normal development" 

 p. 198. The amitotic process is said to be always accompanied in 

 this species by rapid cell multiplication. All of the male germ cells 

 are said to pass through the amitotic cycle, and later divide mitoti- 

 cally. The gist of Wieman's hypothesis respecting the cause of 

 amitosis is expressed in a "nutritive disturbance" resulting from a 

 "reduced oxygen supply" pp. 173 — 174. He further subscribes to 

 Strasse urger's view expressed in 1882 that amitosis in the higher 

 forms represents a survival of a primitive process of cell division, 

 and regards mitosis and amitosis as "extremes of a continuous series; 

 the different configurations of the division figures being due to the 

 different types of metabolism represented" p. 198. 



For fuller reviews of the literature the reader is referred to the 

 papers by Child, by Wieman and by Richards; and to Wilson's 

 "The Cell" pp. 114 to 119 and p. 285, and the "Traite d'Histologie" 

 by Prenant, Bouin and Maillard (Paris; pp. 761 — 767). 



The foregoing brief review of recent literature shows that amitosis 

 is somehow associated with conditions that underlie rapid embryonic 

 growth, neoplastic growths, degeneration and intense functional 

 specialization. Child suggests identification of this condition with 

 inadequate nutrition, Wieman with inadequate supply of oxygen. 



Comparative observations. The only indication of a 

 favorable condition for amitosis in the cells of the epididymis is the 

 specialization in the shape of cilia. If the presence of cilia is a suffi- 

 cient cause for amitosis in the epididymis, then the direct method 

 of division should be the prevailing one in other types of ciliated 

 epithelia. With a view to testing this hypothesis extensive compara- 

 tive observations were made. 



