Studies on Chromosomes 



149 



convincingly by the definite correlation of the spermatocyte- 

 groups with those of the spermatogonia of the same individual. 

 This is shown in the following table, which summarizes the facts 

 thus far observed. 4 



SUMMARY 



Distribution in the whole group 



4 The somatic numbers of the males are in each case determined from the dividing spermatogonia. 

 Those of the female are from dividing cells in various parts of the ovary mainly from the region just 

 above or below the end-chamber some of them undoubtedly folicle-cells, others probably young nutri- 

 tive cells or obgonia. The chromosome-groups from different regions differ considerably in size, but 

 otherwis show the same general characters. With a very few exceptions the number of chromosomes 

 has been determined by the count of several groups from the same gonad, in many cases by the count of 

 a very large number. In many individuals hundreds of perfectly clear equatorial plates may be seen 

 and the evidence is entirely demonstrative. In seven of the males (owing to lack of mitoses, or to defec- 

 tive fixation) the somatic number has been inferred from that shown in the spermatocyte divisions, or 

 vice versa; but with a single exception both numbers have been directly observed in other individuals of 

 the same type. I am therefore confident that the numbers are substantially correct as given. In case of 

 the female, only the somatic numbers can be given, since the maturation-divisions are not available for 

 study. 



