i6 



CYTOLOGY 



CHAP. 



so that the same microscopical picture is interpreted by one cytologist as 

 vacuolation, by another as the unravelling of 'a single twisted thread, 

 and by a third as the intertwinings of two threads. Thus, even in the 

 most obvious cases of thread formation, this is always accompanied by 

 irregularities in the thickness and in the distribution of the conspicuous 





Root tips of Allium cepa. (A, B, C, after Dehorne, A.Z., 1911 ; D, E, after Bonnevie, A.Z., 1908; F, G, 

 after Gregoire, L.C., 1906.) A, D, F, telophase; C, E, G, prophase ; B, resting nucleus. 



chromatin along the inconspicuous linin basis of the thread, and also by 

 outgrowths and anastomoses, which are generally sufficient to conceal 

 entirely in the resting nucleus its essential construction out of compara- 

 tively few long threads. The same factors, acting in telophase at a still 

 earlier stage of thread formation, may easily conceal the true nature of 

 this process, and convert what is essentially an irregular and twisted 

 thread into the appearance of a reticulum. On the other hand, the early 



