440 IV A TA SE. [Vol. VIII. 



Hermann, 1 Flemming^ and others on the formation of the 

 small but perfect spindle at a distance of the nucleus, bear 

 the same interpretation, viz., the co7iversion of the uiaterial of 

 the centrosome into the fibres of the spindle. On the other 

 hand, it may be incidentally observed here, that the forma- 

 tion of the perfect spindle in the substance of the cell- 

 body, at some distance from the nucleus, shows pretty strongly 

 against the view that the contents of the nucleus has any- 

 thing to do with the formation of the spindle filaments. 



The view that places the microsome in the same category 

 with the centrosome throws a further light on the obscure 

 points connected with the formation of the " cell-plate " (Fig. 5, 

 Eq. M.) and the " Zwischenkorper " (Fig. 6, Zh.). 



The " cell-plate " which is formed in the equatorial plane of 

 the spindle of a certain cell, is composed of a series of knob-like 

 enlargements of the filaments. This knob-like enlargement of 

 the filament stains deeply and shows exactly the same micro- 

 chemical reaction as with the microsome and the centrosome. 

 This series of knob-like thickenings have been called by 

 Guignard the " jnierosofnes chivmatiques" on account of their 

 affinity to staining reagents. 



I hold that these thickenings are identical with the cyto- 

 microsomes, and are produced by the spindle filaments /;/ situ. 

 They may be called the eq2iatorial microsomes (Fig. 5, Eq. M.). 

 Morphologically considered, the spindle filament stretching from 

 pole to pole of the caryokinetic figure is nothing but an 

 extremely elongated cytoplasmic filament with but one micro- 

 some in the middle, with two huge microsomes at the 

 extremities. In this respect the spindle filament is directly 

 comparable with any portion of the filament of the aster, in 

 which the microsomes are consecutively arranged, at regular 

 intervals. There is this difference between them, however, 

 that while in the filament of the aster the distance between the 

 two consecutive microsomes is extremely short, in the filament 



1 F. Hermann: Beitrag zur Lehre von der Entstchnng der Karyokinetischen 

 Spindel. Archiv f. mikrosk. Anatomie, Bd. XXXVII, 1S91. 



2 W. Flemming: N'etic Bcitrdge zur Keti7itniss der Zelle. II. Arch. f. mikrosk. 

 Anatomie, Bd. XXXVII, 1891. 



