198 • ROBERT T. HANCE 



14. The conditions found in Oenothera scintillans and the 

 pig agree in practically all details (p. 181). 



15. The chromosomes at the long end of the series are the 

 ones that are chiefly concerned in fragmentation (p. 183). 



16. Fragmentation does not enter the germ line. 



Discussion 



17. Much of the cytological work that has been done on 

 mammals is believed to be faulty due to improper fixation 

 (p. 184). 



18. Previous studies on the pig are reviewed and it has been 

 demonstrated that, although only 18 chromosomes were re- 

 ported, the actual amount of chromatin present is probably 

 the same as found in this investigation. The chromosomes as 

 reported are fused and clumped together in the earlier work; 

 due to poor fixation (p. 185). 



19. The various types of chromosome variation (multiples, 

 deficient chromosomes, the loss of chromosomes and fragmenta- 

 tion) that have been studied recently are briefly discussed 

 (pp. 190, 194 and 232). 



20. It is pointed out that although many of these peculiarities 

 are closely linked with taxonomic differences, the cause of 

 these variations is still obscure (p. 194). 



21. The additional evidence that the present work affords 

 the theory of the individuality of chromosomes is commented 

 upon (p. 196). 



Results of the investigation in brief 



The chromosomes of the soma may fragment but the frag- 

 ments continue as part of the complex. The total amount of 

 chromatin in the somatic cell in which fragmentation has oc- 

 curred is the same as in the spermatogonia. There is no frag- 

 mentation in the germ cells, and the chromosome complex re- 

 mains unchanged. 



