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The nature and distribution of attraction-spheres and 
centrosomes in vegetable cells.! 
JOHN H. SCHAFFNER. 
WITH PLATE XXXIII. 
Introduction. 
The question as to the nature of centrosomes and attrac- 
tion-spheres and their importance in the cell is still in dispute. 
Some hold that these bodies are only temporary accumula- 
tions of the cytoplasm of the cell, while others contend that 
they are permanent organs, which are secondary in import- 
ance only to the nucleus itself. Moreover, the number of 
these bodies in each cell, their movements and manner of di- 
"sion, their action during impregnation of the ovum, whether 
*yTemain on the outside or inside of the resting nucleus, 
and even their action during the process of indirect cell di- 
‘Sion are all questions more or less in dispute. It seems, 
Wever, that from the chaos of opinions enough truth can be 
“overed to enable one to arrive at a safe conclusion in re- 
bard to many questions relating to them. Since the work 
titherto done on plants was more especially in connection 
roductive cells, it was my purpose to work entirely 
with Purely vegetative cells,—to study the existence of cen- 
Somes and attraction-spheres in these cells, to find whether 
‘Ytemain on the outside of the resting nucleus or are in- 
ES ed by the nuclear membrane, to determine the number of 
‘ ; bodies in each cell, and to trace them from the resting 
as through the stages of karyokinesis. In my investi- 
had the assistance of Professor F. C. Newcombe, 
S 
0 ; 
ue °S€ Suggestions are largely due whatever success I may 
Ve attained. 
Historical. 
Discovery, —To Professor E. van Beneden (26)? belongs the 
183 of having discovered the attraction-sphere. In the . 
ie’ he found in the fertilized ovum and the blastomeres 0 
Seas mMegalocephala, at the poles of the nuclear spindle, 
4 4 . = . 4 H 
Tet bution from the Botanical Laboratory of the University of Michigan. 
Ne refer to the bibliography at the close of the paper. 
‘ 4~Vol, XIX—No, Il. ; 
