blackman: the spermatogenesis of scolopendra. 3 



formation of the spindle and its peculiar modification in the division of 

 the first spermatocyte. During the early prophase the centrosomes 

 never rest directly upon the nuclear membrane, but remain at a con- 

 siderable distance from it, and in the later prophase they migrate in 

 opposite directions, until they come to lie very close to the cell mem- 

 brane. From these proceed the astral rays, none of which seem to 

 connect in later stages with the spindle fibres. The linin of the nucleus 

 gives rise to the fibres of the spindle, which, though the poles are trun- 

 cate, are directed respectively toward the two (now double) centrosomes, 

 a condition that is often seen in plant cells. The astral fibres radiating 

 from the centrosomes remain entirely distinct from those of the spindle. 

 Concerning the origin of the chromatin the authors have little to say, 

 since in the earliest stages studied by them the chromosomes were 

 already in the form of distinct elements. At this stage the " nucleolus " 

 has already broken up into several fragments, which are colored red by 

 the Ehrlich-Biondi stain. I should like to mention in this connection 

 that in preparations of three species of Lithobius collected at three 

 widely separated localities, Kansas, Massachusetts, and Bermuda, I have 

 observed that the chromosomes arise from the nucleolus-like body or 

 karyosphere. This is shown in material fixed by various reagents and 

 stained by several methods, including Heidenhain's haematoxylin and 

 the Ehrlich-Biondi triple stain. In a later paper I hope to discuss at 

 length the origin of the chromosomes. 



In a series of short papers from the University of Nancy, P. Bouin, 

 M. Bouin, and R. Collin have dealt with various problems connected with 

 the spermatogenesis of Lithobius, Geophilus, and Scolopendra. The first 

 of these (P. et M. Bouin, '99) is concerned with the presence and evo- 

 lution of certain irregularly formed bodies in the cytoplasm. These the 

 brothers Bouin believe to arise by the breaking down of the astral fibres ; 

 later they undergo a sort of gelatinous metamorphosis, and in the early 

 prophase disappear. Meves und von Korff (:01, p. 482), however, find 

 these bodies throughout the whole period of mitosis of the first sperma- 

 tocyte, although during the later stages they break up into smaller 

 granules. 



In several later papers Bouin and his colleagues have described modifi- 

 cations of the spindle in several species of myriapods — Lithobius forfi- 

 catus, Geophilus linearis, and Scolopendra morsitans — similar to those 

 described by Meves und von Korff. Other results of these authors will 

 be mentioned later at various places in this paper. 



