196 ROBERT T. HANCE 



The individuality of the chromosomes 



It is not my purpose to enter into a full discussion of the 

 theory of the individuality of chromosomes, as Dr. McClung 

 has thoroughly reviewed this subject in a recent publication ('17). 

 I wish merely to add the proof of the present work to that which 

 has already been done. What follows may have more weight 

 when it is said that I began these investigations with the pur- 

 pose of disproving the hypothesis and was forced into the 

 ranks of the 'behevers' by the unquestionable results obtained. 



It has been shown that in the somatic cells the chromosomes 

 which are unfragmented agree in length, chromosome for chromo- 

 some, with those of the spermatogonia, and the relation be- 

 tween the pairs is the same. When the chromosomes break up, 

 the fragments behave as entire chromosomes at division, and 

 the total length of all the chromosomes of the cell is the same 

 as in the unfragmented cells and the spermatogonia. The quan- 

 tity of chromatin is undisturbed. What I have said in regard 

 to the chromosome situation in Oenothera scintillans, in respect 

 to the individuahty hypothesis, may well be said for the similar 

 conditions in the pig. 



Since no chromatin appears to be lost in the processes that are goinja; 

 on in O. scintillans and as the fragments divide as regularly as they 

 did before they were separated it would seem that at least the spirit 

 of the theory of the individuality of chromosomes was maintained. If 

 the theory of the individuality of chromosomes can only recognize a 

 strict morphological continuity then the chromosomes in scintillans 

 lose their individuality through breaking up. If the theory is broader 

 in its scope and admits an individuality not only of whole chromosomes 

 but of the chromatin or chromomeres then the scintillans situation 

 falls within its • limits. It is the latter interpretation of the theory 

 that I believe cytologists hold or are tending toward today. 



SUIMMARY 



Technique 



1. An improved preservation of mammalian tissue has been 

 obtained through the use of Flemming's (strong and weak) 

 solution, to which has been added a little urea and which is 



