6O MARGARET C. FERGUSON 



derm's egg " no ground for a specific kinoplasm." The term, 

 however, is a convenient one and maybe employed consistently, 

 as suggested by Mottier ('oo), by those who do not find in kino- 

 plasm a morphological constituent of the cell, as descriptive of 

 that portion or manifestation of the protoplasm which is active 

 in spindle-formation. 



Nothing has been said regarding the nature of the granular, 

 cytoplasmic condensation from which the achromatic spindle 

 takes its origin. It never has a definite boundary, though it is 

 often very clearly differentiated by its dense granular appear- 

 ance and its strong affinity for stains ; but at certain stages in the 

 division it may be inconspicuous or fail entirely of demonstration. 

 Such a vast amount of literature has accumulated during the past 

 decade regarding the nature and existence of the centrosome and 

 the centrosphere that one feels inclnied to avoid the subject alto- 

 gether. Yet the question may very properly be asked : Is this 

 condensation which forms the center of a system of radiating 

 fibers a centrosphere? It certainly is as clearly an attraction- 

 sphere as some bodies which have been described as such ; but 

 if we accept Wilson's ('oo) definition of the centrosphere, the 

 body under consideration cannot be so denominated, as no cen- 

 trosome has been observed at its center. More deeply staining 

 granules may sometimes be present within the condensation, 

 but these are not considered of any special significance as such 

 granules may be found anywhere in the cytoplasm. 



Karsten ('93) describes the nucleoli in Psilotum as passing 

 out of the nucleus and assuming the role of centrosomes, and 

 Strasburger ('oo) considers that the nucleoli not only contribute 

 material for the formation of kinoplasmic threads, but that they 

 also make active the spindle-forming substance in the cytoplasm 

 in other words, they act as the kinetic centers of the cell. 

 There seems to be no evidence that such is the case here, for 

 the nucleoli, after the condensation has arisen and the spindle- 

 threads have attained considerable length, are morphologically 

 the same as they were before the inception of the spindle. 

 Nemec (*99 ! ) remarks that in the higher plants, where the cen- 

 trosome is not demonstrably present, the entire nucleus may 

 exercise the function of the centrosome. The idea of a diffused 



