LIFE HISTORY OF PINUS 59 



regarding the position of this nucleus at the time of its division. 

 Whether it is due to the origin of the karyokinetic figure, or 

 whether the unusual method of division is attributable to the 

 very eccentric position of the nucleus, I have not been able to 

 determine. It is evident, hov^ever, that the position of the 

 cfenerative nucleus at the time of its division is such that the 

 spindle if extranuclear in origin must of necessity be unipolar, 

 since there is no cytoplasm, or almost none, above the nucleus 

 from which fibers could arise. 



The blending of the linin reticulum with the cytoplasmic 

 network after the disappearance of the lower portion of the 

 nuclear membrane, and the relation of certain portions of the 

 achromatic nuclear reticulum to the ingrowing fibers are such 

 as to suggest an intimate relation between these structures. 

 That the spindle-fibers which originate in the cytoplasm and 

 apparently grow by a differentiation of its network are later fed 

 by the linin of the achromatic nuclear reticulum, there seems 

 little room for doubt. In fact, all the phenomena connected 

 with this division indicate that we are dealing, not with per- 

 sistent cell-constituents, but with different manifestations of one 

 and the same thing. In a word, we find no evidence here of 

 the presence in the cell of a definite kinoplasmic substance. I 

 am aware that these observations are directly opposed to the 

 views of the students of the Bonn laboratory, and many others 

 of the highest authority ; but the relations of nucleus, spindle, 

 and cytoplasm, not only in this division but in those to be 

 described in connection with fertilization, are such, it seems to 

 me, as to render no other conclusion in the case of these divis- 

 ions in Piniis possible. In 1895 Farmer arrived at a similar 

 decision regarding the origin of the spindle in spore-formation 

 in the Uepaiicc^, and Farmer and Williams ('98) in a study 

 of Fitctis " do not regard the kinoplasm as a persistent proto- 

 plasmic structure, but as forming the visible expression of a 

 certain phase of protoplasmic activity." Hertwig ('98) expresses 

 himself as opposed to the view of a special spindle-forming sub- 

 stance in the protoplasm, while Wilson ('99 and '00) states that 

 the astral rays " grow by a progressive differentiation out of 

 the general cytoplasmic meshwork," and he finds in the echino- 



