46 BIOLOGICAL LECTURES. 



Each one of these parts of the attraction sphere has given 

 rise to more or less discussion; but the chief interest lies in 

 that tiny structure, the centrosome. 



More than twenty questions have been asked concerning it, 

 and if any one of you could give a final answer to any one of 

 them, you would aid greatly in solving the problem. 



WJiat is the centrosome ? 



What is it morpJiologically ? Is it one solid body that even 

 with the highest powers cannot be resolved into more than 

 one ? Or is it an aggregation of small bodies ? What is its 

 origin ? Is it of nuclear origin ? — is its substance chromatin 

 or is it nucleolar substance ? Is it of cytoplasmic origin, — merely 

 a condensation of cytoplasmic network ? Is it furnished by the 

 spermatozoon ? Is it a permanent organ of the cell, such as the 

 nucleus ? Is it always in the cell during the resting stage as 

 well as during division, or is it formed anew at the period of 

 division ? 



WJiat is its function? Is its presence necessary to cell 

 division, or is its appearance merely the result of cell division ? 



These are merely specimens of the questions that can be 

 asked, and every one of these opposing questions has been 

 answered in the affirmative, and every one has been answered 

 in the negative, by one or more investigators. They show us 

 how far biologists are from an agreement on this subject. 



If we extend our questions to the attraction sphere, we must 

 ask: Is tJiere such a thing as arcJioplasm in the attraction 

 sphere? Some investigators tell us that archoplasm is not a 

 specific substance in the cell, that it is merely a condensation 

 of the cytoplasmic network, merely a delusion, and that the 

 very term should be dropped from the cytological vocabulary. 

 In the Qgg of Allolobophora foetida this " delusion " can 

 be sharply differentiated from the cytoplasm by differential 

 staining. Assuming that the archoplasm is a specific substance, 

 it is asked : Are the rays of the attraction sphere archoplasm, 

 or are they cytoplasm .'' And each of these questions has 

 been answered in both the affirmative and negative. 



