IOS FRANK R. LILLIE. 



In my paper of 1906, I described and illustrated a naked 

 spindle with centrosomes at its ends, but practically no radia- 

 tions. This spindle was found in an egg that had been centri- 

 fuged about 2,000 revolutions in a minute at a radius of 13 cm., 

 killed in picro-sulphuric acid, sectioned, and stained in Delafield's 

 haematoxylin. At the time, I was not paying special attention 

 to the question of analysis of the karyokinetic figure, and I re- 

 garded the case as typical. 



When I repeated the experiments in the summer of 1906, with 

 special reference to the analysis of the karyokinetic figure, I soon 

 found that the condition of a naked spindle after centrifuging was 

 not typical ; on the contrary, it is extremely rare and excep- 

 tional. Well-developed asters are the rule after centrifuging, 

 though they may exhibit certain asymmetries or other modifica- 

 tions of the normal condition. Either, then, the rays must per- 

 sist in spite of movements of the spindle and passage of granules 

 through them, or the naked spindle must have formed new 

 radiations. 



Presumably the latter process would require time, and it there- 

 fore seemed possible that if special pains were taken to fix the 

 eggs in the shortest possible time after centrifuging, one might 

 find at least a considerable proportion of naked spindles. But 

 this also proved a vain expectation. Typically, astral radiations 

 are well developed after centrifuging ; and this is the case no 

 matter how quickly the eggs are killed, nor whether the speed 

 be high or low, within the limits of the actual experiments. 



I therefore considered the possibility of fixing the eggs during 

 the action of the centrifugal force, but I did not see clearly how 

 to compass this end and so the experiment was never performed. 



I. MOVEMENTS OF THE SPINDLE. 



Every case in which it can be demonstrated that the spindle 

 has moved through the cytoplasm furnishes a test between 

 mitome and centrosome hypotheses. If the visible rays are 

 organic radii attached to the poles of the spindle (mitome hy- 

 pothesis), they must be disarranged by each movement of the latter, 

 and movements of the spindle at different angles to its own axis 

 must produce different characteristic modifications of the rays of 



