1896. THE CELL AND ITS SUPPOSED STRUCTURES. 329 



we arrive respecting the nature of the centrosome, an important 

 principle is involved. It is doubtless simpler to admit the existence 

 of a variety of ' organs ' in the cell ; but does such an admission bring 

 us any nearer to understanding the actual processes of cell-life ? 

 Looking the facts squarely in the face, it is very difficult to maintain 

 the hypothesis of an independent autonomous development for the 

 spindle. Most of the carefully worked out results of recent years seem 

 to point to it as arising as a differentiation out of the normal proto- 

 plasmic structure, and not as the replacing of this by an intrusive 

 centrifugal outgrowth of a special substance surrounding the 

 centrosome. But, just as with this latter body, so also with the 

 spindle, there are differences exhibited by different cells in the degree 

 of mechanical complexity and completeness characterising their 

 spindles. These differences may well be, and, indeed, fundamentally 

 must be, due to physical differences existing between the different 

 protoplasms; thus the ultimate extent of delicacy of adjustment 

 adapted to meet the individual requirements in any given instance 

 would come to depend on the constitution of the protoplasm itself. 

 The same forces acting through different mechanisms will naturally 

 produce dissimilar results. 



Again, the chromosomes themselves present abundant difficulties^ 

 when one tries to form a rational conception which shall embrace the 

 facts now known respecting them. If individuality and permanence 

 be conceded to the chromosomes, how can this be reconciled with the 

 facts of reduction and of fertilisation ? It seems perfectly clear that 

 the reduction, which, so far as is known, always occurs at some point 

 before fertilisation, can be effected in various and radically different 

 ways. And if this is so, how can one grant even the probability of the 

 existence of that complex structure which has been ascribed to the 

 chromosomes as the supposed bearers of the hereditary qualities of the 

 organism ? 



J. Bretland Farmer 

 Royal College of Science. 



2 A. 



