OETHOPTERAN SPERMATOGENESIS 721 



repeated in every cell of every individual of a species, and, in the 

 case of Stenobothrus, in every species of the genus. Further^ 

 this question of form finds its explanation in the relation which 

 each chromosome bears to the archoplasm of the cell — it repre- 

 sents a fundamental matter of cellular organization. 



• Apparently, in interkineses, all this is lost, but the history of 

 the Stenobothrus chromosomes shows that this is not so. The 

 forms of the spermatogonial chromosomes reappear in the grand- 

 daughter cells, and in these two derivatives may be found all the 

 chromosomes of the single cell of the earlier generation, each 

 recognizable by its size and form. This is the common experi- 

 ence of different investigators working upon material derived 

 from the most remote sources and from specimens classified into 

 four or more species. Since the actual act of reproduction is 

 seen in each mitosis, the only conclusion that can be drawn is 

 that these chromosomes of certain definite sizes and forms possess 

 these attributes in the second spermatocytes for the reason that 

 they are lineal descendants of the like series in the spermatogonia. 

 It is justifiable to conclude further that the like series in various 

 species of the genus is the result of the same laws operating over 

 a longer period of time. The animals now in existence within 

 this genus are here because they descended from similar organisms 

 in the past, and their common characters are due to their common 

 ancestry: the chromosomes within the cells of these animals 

 bear the stamp of resemblance in series for the same reason. 

 Indeed the processes of reproduction in the greater and in the 

 less are coincident and form a common problem. 



It causes no confusion therefore to find interposed between the 

 two cell generations with similar formed chromosomes, an inter- 

 mediate one in which these configurations are not present, for 

 the index of these variations is furnished by the position of the 

 fiber attachment. In each case it is possible to identify the par- 

 ticular element by this feature of its organization, in connection 

 with its relative size in the complex. We .are just beginning to 

 understand something of the exactness of chromosome organiza- 

 tion, and the conditions in Stenobothrus furnish one of the most 

 generally recognized cases of it. Attention has been directed 



