4 



248 WALTER S. SUTTON. 



synapsis as it occurs in vertebrates and other forms possessing 

 loop-shaped chromosomes, the union is side by side instead of 

 end-to-end to as in Arthropods. In vertebrates, two parallel 

 longitudinal splits, the forerunners of the two following divisions, 

 appear in the chromosomes of the primary spermatocyte pro- 

 phases. Both being longitudinal, they have been described as 

 equation divisions, but if it shall be found possible to trace one to 

 the original line of union of the two spermatogonial chromosomes 

 side by side in synapsis, that division must be conceived as a 

 true reduction. A number of observations supporting this view 

 will be brought forward in my forthcoming work on Brachystola. 



Again, if the normal course of inheritance depends upon the 

 accurate chromatin-division accomplished by mitosis, it would 

 appear that the interjection, into any part of the germ cycle, of 

 the gross processes of amitosis could result only in a radical devia- 

 tion from that normal course. Such an occurrence has actually 

 been described by Meves, McGregor and others in the primary 

 spermatogonia of amphibians. In these cases, however, it ap- 

 pears that fission of the cell-body does not necessarily follow 

 amitotic division of the nucleus. I would suggest, therefore, the 

 possibility that the process may be of no significance in inheri- 

 tance, since by the disappearance of the nuclear membranes in 

 preparation for the first mitotic division, the original condition is 

 restored, and the chromosomes may enter the equatorial plate 

 as if no amitotic process had intervened. 



There is one observation in connection with the accessory 

 chromosome which deserves mention in any treatment of the 

 chromosomes as agents in heredity. This element always di- 

 vides longitudinally and hence probably equationally. It fails to 

 divide in the first maturation mitosis, in which the ordinary chro- 

 mosomes are divided equationally, but passes entire to one of the 

 resulting cells. In the second maturation division, by which the 

 reduction of the ordinary chromosomes is effected, the accessory 

 divides longitudinally. 2 



1 It is of interest in connection with this question that there occurs regularly in 

 each of the spermatogonial generations in Brachystola a condition of the nucleus 

 which suggests amitosis but which in reality is nothing more than the enclosure of 

 the different chromosomes in partially separated vesicles. Cf. Sulton, W. S. , "The 

 Spermatogonial Divisions in Brachytola Magna," Kans. Univ. Quart., IX., 2. 



2 The chromosome x of Protenor, which of all chromosomes in non-orthopteran 



