204 KANSAS UNIVERSITY SCIENCE BULLETIN. 



integration of the chromatin is always into a definite number 

 of chromosomes in the individual, in the species, and sometimes 

 in an entire family. From this the precision of organization in- 

 herent in the chromatin may be inferred. Again, throughout 

 all the complications of the mitotic division every effort is ap- 

 parently put forth by the cell to secure an accurate division of 

 the chromatin. This suggests the primary importance of the 

 chromatin and hints strongly of differential organization. 



If now we turn from cells in general to the special category 

 of germ-cells we find very much more evidence for our belief 

 that the chromosomes are the determinants of characters and 

 that they are qualitatively different. From this source we 

 learn that normally, for the production of a new organism, two 

 cells are required, and that the only feature of equivalence 

 between them is in the chromosome complex, which in each case 

 is a duplicate of the other. Not only are these morphologically 

 equivalent groups of chromosomes, but they are also physio- 

 logically equal, for either complex alone may condition de- 

 velopment in the same way, as is shown by parthenogenesis 

 and merogony. Further evidence of this independence and 

 equivalence of the chromosomes is furnished by the history of 

 the cells of which they are a part, for step by step they go 

 through the same preparation of maturation, and the particu- 

 lars wherein they show resemblances are always those of chro- 

 mosome behavior, no matter how much the other elements of 

 the cell may differ. 



While either the paternal or maternal chromosome complex 

 in a cell is sufficient to condition the development of all the 

 characters of the organism, the absence of any one chromosome 

 of the group results in the non-development of some body 

 characters. Such, at least, seems to be the conclusion that must 

 be drawn from the work upon polyspermized eggs. It there- 

 fore appears very probable that the chromosomes are quali- 

 tatively different. Very strong additional evidence to support 

 the view that the chromosomes are qualitatively different, and 

 a duplicate series when present in the normal number, is af- 

 forded by the parallelism between the behavior of the chromo- 

 somes in maturation and fertilization, and the segregation of 

 Mendelian characters in hybrids. 



Let it be granted from the facts adduced that the chromo- 

 somes are the controlling factors in development, then how can 

 we explain their action, how correlate them individually with 



