THE SPERMATOGENESIS OF THE MYRIAPODS. IQI 



as the criterion of the synapsis or pseudo-reduction, but Mont- 

 gomery, 'oi, apparently abandoning his former views upon the 

 subject, asserts, probably with very good reason, that in reality 

 synapsis occurs at a considerably earlier stage. In Pcripatns, 

 'oo, he is able to study the manner of this union of the chromo- 

 somes and from observations seems to have good grounds for 

 the assertion that synapsis is accomplished by an end to end 

 union, in pairs, of entire chromosomes during the retrogressive 

 stages of the telophase of the last spermatogonial division. 1 



In Scolopcndra, owing to the small size of the spermatogonia 

 and the extreme minuteness of the spermatogonial chromosomes, 

 as well as their larger number and close aggregation during the 

 telophase, the manner of union and the details of the process cannot 

 be studied ; but it can be stated with the greatest certainty that 

 pseudo-reduction occurs during the telophase of the last sperma- 

 togonium, and is completed before the reconstruction of the 

 nuclear membrane. At the time of the formation of this struc- 

 ture, the nuclear space is occupied by sixteen elongated seg- 

 ments of chromatin and resembles very closely the nucleus in 

 insect cells with the exception that the nuclear area is much 

 larger in proportion to the amount of chromatin and thus the 

 segmented character of the chromatin is evident (Figs. 5 and .6). 

 Besides these sixteen diffuse segments of chromatin, the acces- 

 sory chromosome is also plainly visible within the nucleus. It 

 still preserves its distinctive characteristics and has changed very 

 little from its condition during the preceding division. To be 

 sure, it has increased in size as have all parts of the cell, but this 

 increase may all be referred to natural growth. This element 

 takes no part whatever in the process of synapsis. During the 

 spermatogonial stages it is a simple chromatic structure and in 

 the following spermatocyte period it still retains its univalent char- 

 acter when all of the other chromosomes are bivalent. 



The completion of cell division and the union of the chromo- 

 somes occurring during the telophase have occupied considerable 

 time, as is shown by several facts. Cells in various stages of the 



! A late paper by W. S. Sutton upon "The Morphology of the Chromosome 

 Group in Brachystola magna" contains further and much more convincing proof of 

 the truth of this process. Mr. Sutton is able to trace plainly the union of the chro- 

 mosomes and to show that it is undoubtedly an end-to-end union of entire elements. 



