EEPRODUOTIVE ELEMENTS IN APUS AND BRANCHIPUS. 263 



cannot strictly divide the tube into ascending zones. When 

 the ordinary somatic division has come to an end spermato- 

 genesis sets in among the cells lining the hollow of the tube. 

 These somewhat minute elements rapidly increase in size, and 

 their nuclei pass into a spirem, with a peculiar and charac- 

 teristic grouping of their chromatic elements all on one side, 

 just as in Hermann's beautiful figures of spermatocytes in 

 the salamander (fig. 3).^ 



Sometimes before, and always during the course of these 

 changes, bodies answering to the centrosomes in all peculiari- 

 ties except their number, which is abnormally great, make 

 their appearance in the angular mass of protoplasm at the bases 

 of the characteristic cells represented in figs. 1 — 4, a. 



Merely for the sake of clearness, and to keep these bodies 

 out of confusion with the true and enormous centrosomes ap- 

 pearing later, as well as to separate them from another type of 

 body, to which T shall have to refer at length, I have provision- 

 ally collected these bodies under the term pseudosomes. 



As the spermatogenesis proceeds, the lop-sided chromatic 

 arrangement of the spirem rapidly gives place to ten chromo- 

 somes, all arranged on the nuclear periphery, and these ten 

 chromosomes in turn become transversely constricted to form 

 the well-known dumb-bell elements (figs. 8 — 12), so that we 

 have ten double or twenty single chromosomes, which rapidly 

 arrange themselves in the disc-like equatorial plate seen in 

 optical section (fig. 11). 



At this period of the metamorphosis (Flemming's meta- 

 kinesis) a number of most remarkable bodies make their 

 appearance, more or less exclusively related to the cell peri- 

 phery, but connected one to another and to the inner group of 

 chromosomes by fine strands, which remain uncoloured by re- 

 agents ; and, as their relation to these fine threads suggests the 

 nodal points in a net, I have termed them dictyosomes 

 (figs. 11—13, d). 



The constriction between the dumb-bell-like heads of the 

 chromosomes becomes more and more pronounced, and they 

 ^ ' Arch. f. mikros. Anat.,' Bd. xxxvii. 



