100 bulletin: museum of comparative zoology. 



Eiern, auch mit den starksten Vergrosserungen mir als kleine, nicht 

 weiter analysierbare Punktchen erscheinen." 



What structure in Scolopendra heros answers the requirements of such 

 a centrosoine ? It is at once very plain that the only structure of this 

 class which is present at all times is the deeply staining body. This is to 

 be found at all stages of the development of the testicular cells, and does 

 not vary at any time in its staining reactions. In the prophase, when 

 the centrosomes are moving in opposite directions upon the nuclear mem- 

 brane, there is no sign of any outer sphere about them. The astral rays 

 converge toward these small dark bodies and can be plainly seen to come 

 in direct contact with them. Later in the prophase, when a surrounding 

 zone is beginning to appear, the rays can be plainly seen to penetrate 

 this zone in their course toward the central body. In the prophase of 

 the second spermatocyte this structure lies apparently naked in the cyto- 

 plasm, and a like condition also exists in the telophase of the second 

 spermatocyte and in the early spermatids. But " das wichtigste Kenn- 

 zeichen " is the relation of the centrosome and the astral rays. As 

 quoted above, the body with which the rays come into direct contact is 

 the centrosome. It has been shown that in the prophase the rays are 

 directly continuous with the dark central bodies, even after the surround- 

 ing sphere has become visible. The same is true in the late metaphase 

 and anaphase of the small spermatocyte. Here, when the outer sphere 

 has decreased in size, the rays can plainly be seen to converge in the 

 central body. During the early metaphase, however, and in the telo- 

 phase they cannot be traced through the outer zone on account of its 

 much larger size and greater density at these periods. 



The centrosome according to Boveri should not betrin to divide before 

 the metaphase, and should not complete this separation until consider- 

 ably later. The central bodies in the spermatocytes of Scolopendra show 

 their first sign of division at the time of their divergence in the prophase, 

 but this division is never completed before the anaphase and in the small 

 spermatocytes does not occur until even later. According to Boveri, 

 therefore, these bodies should be called centrioles. But centrioles are so 

 extremely minute that even in the largest cells and under the highest 

 magnification they appear as mere points, incapable of further analysis. 

 The central bodies in my material do not fulfil this requirement as 

 well as they do that of Boveri's centrosome. They are not small points 

 incapable of further analysis, but are of considerable size, and at all times, 

 except during the vesicle stage, when completely inactive, of a granu- 

 lar or spongy consistency, as is the case with the central body in 



