Karyokinesis 329 



transmitted by the nuclear chromatin, in a succession of 

 predetermined events; each group of events controlled by 

 a segment or cluster of that substance which we have likened 

 to a bead on a string; so that when all the beads split down 

 the center and the string becomes two strings, then each 

 string has all the qualities of the parent. Quantity seems to 

 be provided by power of assimilation and growth, that is, 

 each beadlike group constituting a nucleus, seems to have 

 the power of growth by assimilation to replace in cell size, 

 the loss by division, enough to resume a size permitting of 

 new division. Next it is observed that this growth power 

 runs a definite course; and the end of that course is reached, 

 after a regular development, constant for all members of 

 a species. For example a certain species divides so many 

 times (perhaps sixteen) without change of character, the 

 nucleus distributing each time all the same chromatin quali- 

 ties ; and although size is perhaps not evenly maintained there 

 is growth CO prevent too great depreciation. One cell 

 becomes two then each becomes two; making four. These 

 four are arranged usually as four soft balls would lie in close 

 contact on a table; then each of these four divides, this 

 time in the table plane and producing upward and down- 

 ward, taking the line of least resistance for equal division; 

 and making a doubled plane group of eight cells, then each 

 again divides outward and there are sixteen. Now at this 

 stage (in some types) the new development appears. All 

 of the sixteen cells divide again; but one of them does so 

 by parting the nucleus so that the descendant cell takes, not 

 a split half of every knot or bead, but a portion only of 

 the length of the string- It may well be that the first knot 



