588 CLARENCE E. McCLUNG 



6. Despite this individual variation in the composition of the 

 mitotic units, there is no loss in the total morphological elements 

 of the specific complex, or departure from the usual habits of 

 synapsis and segregation of homologous elements. 



7. The maintenance of the original complex in the presence of a 

 variable number of mitotic units results from associations of 

 these to produce others of higher valence. 



8. Where variation between individuals exists for any one cell 

 generation, it is the result of differences in association between 

 certain definite mitotic units. 



9. Such variations are not indefinite, but occur in a fixed order 

 between certain units. 



10. The occurrence of associations between units of lower order 

 into those of a higher results from the operation of a common 

 integration principle. 



11. The union of homologous chromosomes to produce te- 

 trads is temporary and is terminated in one of the following 

 maturation divisions ; multiples of non-homologous chromosomes 

 are permanent for the individual and the union does not end in 

 either maturation mitosis. 



12. Associations in the first spermatocyte of a higher order 

 than tetrads are the result of lower associations which are per- 

 sistent throughout all cells of the individual. 



13. Associations into tetrads in the first spermatocyte occur 

 between homologous chromosomes. 



14. Higher associations than tetrads in the first spermatocyte 

 are necessarily non-homologous. 



15. Associations may be complete and persistent, or only 

 approximations. 



16. Associations may be complete in parts of chromosomes and 

 incomplete in other regions. 



17. The point of union between associated units in metaphase 

 is at the ends of the chromosomes. 



18. In telomitic chromosomes this is at the point of fiber 

 attachment. 



19. Atelomitic chromosomes of unit value have not yet been 

 observed in multiples, except in that part of the tetrad of Mer- 

 miria not joined to the accessory chromosomes. 



