BLACKMAN. — SPERMATOGENESIS OF THE MYRIAPODS. 491 



obtained with Heiclenhain's haemotoxylin used either alone or with 

 Conijo red as a counterstain. Sections thus stained were used for 

 all detailed studies of the cell structures. For micro-chemical tests, 

 Flemming's three-color stain and the Ehrlich-Biondi mixture were 

 used, the results obtained with the latter being especially satisfactory. 



Observations. 



The testis of Lithobius consists of a single unpaired sac tapering at 

 the anterior end, where it ends blindly, and also tapering shghtly at the 

 posterior end, where it is directly continuous with the vas deferens. In 

 adults, which were used exclusively in this study, the spermatogonia 

 are found only at the periphery of the testes. They are small spindle- 

 shaped cells containing oval nuclei (Plate 1, Figure 1), and are similar 

 in all respects to the spermatogonia of Scolopendra, with the exception 

 that each nucleus contains two karyospheres instead of one. These 

 karyospheres consist largely of chromatin, as is shown by their reaction 

 to stains. They are stained black in iron-haemotoxylin, and after treat- 

 ment with the Ehrlich-Biondi mixture they are colored green, while all 

 other cell structures assume a red tint. The remaining portion of the 

 nucleus is occupied by a network of linin fibres, which stains as lightly 

 as does the cytoplasm outside of the nucleus. 



The constancy with which two karyospheres, and never more than 

 two, occur in the spermatogonia of Lithobius mordax has led me to ask 

 what significance this may have. When we consider that there are 

 always two karyospheres in the spermatogonia, and never more than 

 one in the spermatocytes of this species, the explanation suggests itself 

 that one of the spermatogonia! karyospheres may represent the chromo- 

 some group derived from the mother, while the other one is made up of 

 paternal chromosomes. However, it would seem impossible to obtain 

 proof of this, and the suggestion is made merely as an interesting possi- 

 bility. Furthermore, this condition is constant only for Lithobius 

 mordax, while in Lithobius sp. 1 the number of karyospheres in the 

 spermatocytes is often as great as four. At the beginning of the active 

 prophase of the spermatogonia! mitoses in Lithobius, the chromatin 

 leaves the karyospheres and becomes arranged throughout the nucleus 

 in the form of a large number of fine granular threads (Figure 2), each 

 one of which represents a chromosome. The number of these segments 

 at this stage is so great, and the nucleus is so small, that it has been 

 found impossible to count them ; but from counts of the chromosomes 

 during the spermatocyte stages, it may be inferred that the number of 

 these granular threads found in the spermatogonia is forty-eight, so 



