THE CELL AND ITS CONSTITUENT STRUCTURES. 165 



bodies in themselves ; consequently, there must be present 

 in each of the reduced chromosomes all the particles which 

 were in the two originals. But it is clear that on this view 

 no real reduction has taken place at all ; the new chromo- 

 some cannot be represented as C, but it is still AB and so 

 on through the successive generations — this however is ob- 

 viously impossible. But if it be urged that in the new 

 chromosome, AB, there is a sort of struggle for existence 

 amongst the hereditary units, half of which become ulti- 

 mately extinguished, we are carried at once into the realms 

 of pure fancy, and besides, why should not the units have had 

 their fight out before ever the chromosomes were differen- 

 tiated so that each chromosome in the reduced nucleus 

 merely contains the survivors ? But there is absolutely no 

 evidence that any part of the nucleus does atrophy during 

 these, rather than in other divisions ; indeed, the reproduc- 

 tive nuclei are characterised by their specially large size. 

 Hertwig has tried to get over the difficulty by declining to 

 recognise any such structural arrangement as Weismann 

 and his adherents postulate ; for him the essence of the 

 process lies in the rapid reduction of the nucleus to one 

 fourth of its original bulk, by divisions at right angles to 

 each other. Thus from Hertwig's point of view it does not 

 signify whether these divisions are both longitudinal, or 

 whether one is transverse, — the final result is the same. 



And really this seems about to express our present know- 

 ledge on the subject. But if we accept such a view, it is 

 difficult to see how we can help giving up a belief in the 

 complicated architectural structure of the chromosome of 

 which each constituent has been supposed to have its special 

 position allotted to it, and its special part to play in the 

 development of the organism. We come very near regard- 

 ing the chromosome, complicated as it may well be in 

 the structure of its molecules or molecular aggregates, as 

 nevertheless intrinsically symmetrical. Heredity is then 

 the outcome of its constitution as a whole, and is not the 

 expression of activities residing in, and apportioned to, 

 respectively discrete parts of it — assuming of course that 

 the chromosomes arc really the organising directors which 



