The Spermatogenesis in Pentatoma up to the Formation of the Spermatid. 41 



to 6, SO that the number at that time is the same as in the dense 

 spirem stage which is now being considered ; hence we must conchide 

 that as many chromosomes become differentiated out of the reticulum 

 of the resting cell, as pass into it. But this is no proof of a retention 

 of the individuality of the chromosomes during the resting period, 

 since, with the facts at hand, we may as justifiably conclude that a 

 nucleus which enters the rest stage with e. g. 3 chromosomes would 

 enter the spirem stage with 4, 5, or 6 chromosomes, as that it would 

 pass into the spirem stage with 3 chromosomes. 



It is important to note that the number of the chromosomes in 

 the dense spirem stage is always less than the definitive number 

 found in the two spermatocytic divisions, namely 7. Thus one or 

 more of the 3 — 6 chromosomes of the dense spirem must segment 

 in order to produce the definitive number ; and , as will be shown, 

 this segmentation process may be readily observed in the majority 

 of nuclei about the commencement of the loose spirem stage. 



The dense spirem is of shorter duration than the loose spirem stage. 



From the resting stage of the 1st spermatocyte to the formation 

 of the spermatid, there is absolutely no longitudinal division of the 

 chromosomes. I have studied hundreds of nuclei in these stages, 

 and at the first with the hope of finding a trace of such a process, 

 but observation shows that all divisions of the chromatin elements 

 are transverse divisions ^). 



The long, slender chromosomes of the dense spirem stage gradually 

 shorten and thicken (Figs. 116 — 118), until a stage is reached which 

 corresponds to the loose spirem of other objects (Figs. 119 to about 

 122). At the same time the chromosomes become smoother and 

 almost homogeneous in appearance. At the commencement of this 

 stage, as in the preceding, the number of these elements varies from 

 3 to 6. But as the process of shortening and thickening continues, 

 transverse segmentation of one or more chromosomes takes place 

 (Figs. 124—129), until finally 7 chromosomes result. This segmentation 

 is a transverse constriction, not always at the middle of a chromo- 

 some ; the constriction does not occur simultaneously on all chromosomes, 

 nor yet it is confined to a particular period of the loose spirem. 

 There is great irregularity in regard to the time of this division, if we 

 take the form of the chromosomes as a criterion of the different stages. 

 And as the figures show, there is throughout the prophase of the 



1) After this paper had been sent to press, I found other pre- 

 parations evidences of a longitudinal splitting at this stage ; but the 

 split subsequently disappears. 



