M'CLUNG : SPERMATOCYTE DIVISIONS OF THE ACRIDID.E. 83 



raoii to all insects. The work of Paulmier makes it almost certain 

 that the processes prevailing in the Orthoptera also obtain in Hem- 

 iptera. The rings and crosses tigured by many investigators in plant 

 and animal cells might easily be referred to some structure of this 

 character. 



Reference was made on an earlier page to the conclusive evidence 

 ottered by the ring figures with regard to the character of the first 

 spermatocyte division. This, I think, cannot be disputed. The 

 rings, with the point of cross-division to which the threads are at- 

 tached indicated by a slight projection, come to lie in the equatorial 

 j)late. With the contraction of the fibers the halves of the rings sep- 

 arate more and more, until at the point of final separation the result- 

 ing figure differs in no marked degree from that of the rod type. 



If the chromo.somes of the spermatocytes are formed from the 

 spireme thread Ijy one longitudinal and one cross-division, it might 

 naturally be supposed that it is a matter of little moment which of 

 these separations occurs first. Indeed, it might be thought that the 

 chromosomes could divide indiscriminately in the two spermatocyte 

 divisions, some splitting longitudinally, and some across, in the first 

 spermatocyte mitosis. Such an occurrence has, in fact, been described 

 by some authors. 



From my studies of insect spermatogenesis, I am led to believe 

 that such a i^henomenon rarely, if ever, occurs. On the contrary, the 

 chromosomes manifest such a constancy of habit as to indicate some 

 fundamental principle in the order of their divisions. What this may 

 be is not now apparent, but it is none the less real, I think. Owing 

 to the peculiar changes undergone by the chromosomes in the first 

 spermatocyte mitosis, it is conceivable that the diverse accounts of 

 different authors may be due to faulty observations upon unfavorable 

 material. Certainly I should ascribe great constancy to the sequence 

 of the divisions, for all manifestations of cellular activity point to defi- 

 nite and characteristic changes in the nuclear elements. I cannot, in 

 the light of my present studies, subscribe to any theory which ex- 

 plains the division of the chromosomes as one of mere mass separation. 



A teloijhase of the first spermatocyte division is represented in Fig. 

 23. Here it will be noticed that the diads have become grouped 

 together, indistinguishably, into a mass. There"is, however, no reason 

 to believe that they, in any way, lose their identity. There is no such 

 thing as a resting stage between the two spermatocyte divisions. As 

 soon as the archo^jlasm has had time to distril)ute itself in the daugh- 

 ter cells and these have become separate^and distinct individualities, 

 the second spermatocyte division figure is formed. In it, we note 

 just such elements as appear in the anaphases of the first spermato- 

 cyte. 



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