THIRTEENTH LECTURE. 



ORIGIN OF THE CENTROSOME. 



S. WATASfi. 



IF we judge the significance of any biological discovery by 

 the amount of new literature which it has called into existence, 

 the discovery of the centrosome must be considered as one 

 of the most important events in the history of the cell-theory. 



A glance at the cytological literature of the present day will 

 show to what a large extent the attention of biologists is being 

 devoted to the elucidation of this structure. Indeed, as has 

 been truly observed, if there is one feature by which the cyto- 

 logical literature of the present may be distinguished from 

 that of some years past, it lies chiefly in the fuller recognition 

 given to this structure. Robert Brown's discovery of the 

 nucleus in the plant cell paved the way to the formulation of 

 the cell-doctrine by Schleiden and Schwann, who made the 

 nucleus ("cytoblast ") the soul of their famous theory. The 

 discovery of corpuscules centraux by E. van Beneden in the 

 animal cell, or centrosomes, as they have been subsequently 

 called by Boveri, has led to an activity unparalleled in the 

 recent history of the cell doctrine. Professor Flemming's re- 

 mark that the discovery of the centrosome marks as important 

 an epoch in the history of biological science as did the discovery 

 of the nucleus, seems certainly justified. 



The questions naturally arise, What is the centrosome ? 

 Is it a unique organ of the cell equal in importance to the 

 nucleus or the cytoplasm, as claimed by the discoverer ? Does 

 it occur in every cell ? What is the exact part which the cen- 

 trosome takes in the division of the nucleus ? What part does 

 it play in the process of fecundation ? What bearing has this 

 new organ of the cell upon the phenomena of heredity ? 



