BLACKMAN. — SPERMATOGENESIS OF THE MYllIAPODS. 499 



species of Scolopendra (Blackman, :01, :05, :05*; Bouin, "•03, :03*) the 

 spermatocytes in the vesicle stage are of two distinct tj^ies as to size. 

 In Lithobius, however, while there is considerable variation in the 

 sizes of the cells during the vesicle stage, no such great differences 

 exist, and the cells cannot be divided into two types on this basis. 



The cells in the vesicle stage of the three species of Lithobius are 

 quite similar to one another as regards the extra-nuclear portion, but 

 differ considerably in the structure of the nucleus, so much so that 

 the species may be readily identified by this alone. The differences 

 existing between Lithobius mordax and L. multidentatus are less ap- 

 parent than those between either of these and the Bermuda species, yet 

 very little study is necessary for identification. The greatest of these 

 specific differences are seen in the structure of the karyosphere, but the 

 condition of the achromatic structures also varies in the three species. 



What may be taken as the typical appearance of the nucleus in 

 Lithobius mordax is shown in Figure 10. The karyosphere is stained 

 an intense black with haematoxylin and green with the Ehrlich- 

 Biondi mixture, showing that it is rich in chromatin. However, in 

 many sections in which the decolorizing has been carried further, the 

 entire karyosphere does not take the chromatin stain, thus showing 

 that this body is not made up entirely of chromatin, as is that of 

 Scolopendra heros, but contains nucleolar material also, as do the 

 similar structures in Scolopendra subspinipes and Scutigera forceps. 

 A karyosphere of this sort is shown in Figure 9. Here the chromatin 

 is arranged in the form of a network of anastomosing strands which are 

 embedded in the nucleolar substances. No portion of the nucleus 

 except the karyosphere contains any chromatic material. The con- 

 spicuous deposits which form an irregular mantle around the karyo- 

 sphere are very evidently achromatic material, as is shown by their 

 staining reactions. 



In Lithobius multidentatus the karyosphere is much like that just 

 described. The chief difference lies in the fact that here the amount 

 of chromatin to each cell is considerably less. Thus the karyosphere 

 is not usually stained so black and the nucleolar portion is more evi- 

 dent (Figures 11, 12, 13). " It is also true that the chromatin is usually 

 found only on the periphery of the karyosphere outside the nucleolus, 

 resembling in this respect Scolopendra subspinipes. The deposits of 

 achromatic substance in the nucleus are much less abundant and are 

 in more definite bodies, thus allowing more of the linin network to be 

 seen. 



The nucleus in Lithobius sp. 1 differs from that of either of the two 

 species described in several particulars. There are no indefinite 



