NUCLEOLI IN EUSCHISTUS VARIOLARIUS. 22Q 



logical basis for conclusions or to put conclusions to a morpho- 

 logical test, and the idiochromosomes seem to offer a fruitful test 

 of the theoretical value of longitudinal and transverse divisions. 

 In order to retain our faith in the special significance that has been 

 attributed to the longitudinal and transverse divisions we are 

 driven to the inconsistency of accepting the evidence in the case 

 of oneidiochromosome, and disclaiming it for the other --though 

 the evidence in both cases is equally strong. If, on the other 

 hand, we accept the evidence and at the same time retain faith in 

 the theory, we are forced to admit that the sister cells of the 

 first division are also dimorphic and we have a so-called reduction 

 division of one of the idiochromosomes of the first spindle as surely 

 as we have a reduction division (the separation of the two idio- 

 chromosomes) in the second spindle, we thus have a somewhat 

 similar phenomenon occurring in both spindles. 



We have a number of photographs demonstrating both sper- 

 matocyte divisions and also a large number showing the sperma- 

 togonial, oogonial and embryonic chromosome groups several 

 hundred in all, but the publication of these must be reserved for a 

 separate paper, where we shall aim to make a very full compari- 

 son of these chromosomes, giving especial attention to the groups 

 that have not been presented in the papers which advocate the 

 sex-determination hypothesis. We believe that these groups 

 are of special value that we have no right to ignore exceptions 

 because they do not fall in line with certain theories. The trite 

 claim that exceptions prove the rule loses its force when enough 

 exceptions are found to challenge the rule. A careful examin- 

 tion of our preparations makes it possible to select chromosome 

 groups which exactly fit a given theory, but many groups can 

 also be found that are a serious menace to these theories, while 

 on the other hand they present no difficulties to the conception 

 of those who regard the number, size and form of the chromo- 

 somes as inherited characters the expression of cell activities 

 rather than the cause. 



January, 1909. 



