470 E. ELEANOR CAROTHERS 



unaltered from parent to offspring it is easily seen by comparing 

 the complexes of the seven sons with each other and with that 

 of the father that pair number 7 was atelomitic in the mother, 

 pair number 8 was telomitic and pair number 1, which is hetero- 

 morphic in the father and also in three of the sons and telo- 

 mitic in four, must have been telomitic in the mother. 



DISCUSSION 



Since the rediscovery of Mendel's laws, cytologists have accu- 

 mulated a mass of evidence demonstrating the parallelism 

 between the behavior of the chromosomes and the physical 

 mechanism necessary for carrying into effect the known laws of 

 heredity. The existence of the chromosomes in a duplex size 

 series, the union of the members of a pair at synapsis, and their 

 separation during one of the maturation divisions are about as 

 clear evidence as could be expected. 



The writer in 1913 was the first to report the occurrence of 

 homologous chromosomes within a species which could be identi- 

 fied one from the other, owing to a size difference, and to show 

 that the members of this pair segregate freely in relation to the 

 accessory. Wenrich ('14), Voinov ('14 a), and Robertson ('15) 

 reported similar conditions in other Orthoptera. All of these 

 works, however, dealt with the distribution of a single pair of 

 homologues in regard to sex, since the accessory in these forms 

 marks the male-producing from the female-producing sperma- 

 tozoon by passing undivided to one pole at the first maturation 

 division. In my work on Trimerotropis, summarized at the 

 beginning of this paper, the same principle of random segrega- 

 tion was shown to apply to three of the eleven euchromosome 

 pairs. Mr. Robert L. King, working in our laboratory on a still 

 more favorable species, has been able to extend these observa- 

 tions considerably further. 



Since the form of a given homologue is constant for the indi- 

 vidual, the segregation of the homologues of a particular tetrad 

 and the independent assortment of homologues from several 

 different tetrads was clearly established by the intensive study 

 of chosen individuals. The points which remained to be deter- 



