I 68 GRACE MEDES. 



be two methods of division ; for the more nearly the cell ap- 

 proaches the metaphase, the more nearly the spindle extends 

 through its central axis. 



The fibers of the spindle, when first formed, are short and the 

 ends converge to a point in the centrosomes, which, at this period, 

 do not lie upon the cell-wall, but retain their position in the cyto- 

 plasm (Fig. 1 6). However, the centrosomes gradually move 

 apart and come to lie on the cell wall at opposite sides of the 

 cell. Meanwhile, the chromosomes have taken up their position 

 in the equatorial plate and the spindle fibers extend directly 

 through the center of the cell. They do not now, however, ex- 

 tend from centrosome to centrosome, but lie free in the cytoplasm 

 with ends toward these bodies. Their extremities, while converg- 

 ing somewhat, do not meet in a point. Blackmail, '01 (Scolopcn- 

 dra Jicros), described a condition closely resembling this during 

 the formation of the spindle. The centrosomes, however, are 

 upon the nuclear membrane at the time it begins to disappear, 

 but the formation of the spindle and its appearance in early stages 

 closely resembles that found in Scutigcra. As the centrosomes 

 recede toward the cell-wall, the spindle fibers remain united at 

 the same point (the "apical point") from which center of con- 

 vergence parallel linin strands extend to the centrosome, while 

 from around these latter emerge the astral rays. Meves and von 

 Korff, '01 (Lithobius forficatus), describe conditions more closely 

 resembling those found in Scutigera after the formation of the 

 spindle is established, although during this process, the similarity 

 is not so close. Before the disappearance of the nuclear mem- 

 brane, the centrosomes, surrounded by the centrosphere, have 

 already taken their place upon the cell-wall. During the meta- 

 phase, he describes them thus : " Die Spindelfasern liegen in einer 

 hellen Substanz (wahrscheinlich Kernsaft) eingebettet. Nach 

 den Polen zu konvergieren sie etwas ; ih re Enden sind aber 

 nicht mit einander vereinigt, sondern horen frei auf ; diejeniger 

 Strahlen um die beiden Central-korperpaare welche direkt auf 

 die Enden der Spindelfasern zu verlaufen, treten mit diesen allem 

 Anschein nach nicht in Kontinuitat." 



This mutual independence of the spindle-fibers and the astral 

 rays in Scutigcra is the more clearly shown by the great dis- 



