STUDIES OF REPRODUCTIVE ELEMENTS : IT. 3Q5 



not in reality take place simultaneously, but by a succession of two 

 divisions rapidly following one after the other. 



3. Spindle stage : — In my paper for Prof. Weismann's birth-day 

 celebration I have given a figure of a nucleus and an archo])Jasm in 

 the latter of which could be observed a (;lear space next the nucleus. 

 This space was in apjmrent communication with the interior of the 

 nucleus. Since then I have been enabled to find a number of fibres 

 in this s)»:ice (Fig. 40), but the existence of any communication be- 

 tween tliese fibres and the interior of the nucleus can not with 

 certainty be made out. The archoplasm becomes elongated and foims 

 a very Itu'ge spindle. This corresponds undoubtedly with the central 

 spindle of HeniKuni, as stated above, but will be called the arcik^- 

 PLASMIC SPINDLE, in distinction from other spindles îdi-eady de- 

 scribed in karyokinetic divisions of other animals and whose origin is 

 still under discussion; while the fibres of this spindle will be 

 called the central eibres, for reasons stated below. At first the 

 archoplasmic spindle lies tangentially on the surface of the nucleus, 

 but soon assumes a curved figure, depressing at the same time the 

 nuclear wall. In consequence of tliis the nucleus takes a broad 

 C-shaped figin-e, in the concavity of which the archoplasmic spindle 

 lies. A notion of these stages may be gathered from Figs. 3, 21, and 

 24. The chromosomes wliich, at the stages of Figs. 45, 4G, 4(S, &c., 

 are seen radiating from a siiigle point, become with the division 

 of the archoplasm separated into two masses, one attached to each end 

 of the spindle. The archoplasmic spindle elongates and the nucleus 

 assumes the form represented by Figs. 20, 35, 36, 49, and 52. 

 Fig. 35, prepared from specimens killed with Flemminijs fluid and 

 stained with Böhmers hematoxylin, represents the division of tlie 

 nucleus in a dividing individual. The nucleus assumes more or 

 less the shape of a dumbbell, and the archoplasms at both ends 



