SEGREGATION OF HOMOLOGOUS CHROMOSOMES 491 



through the winter out of doors and even the adults endure 

 great extremes of temperature. The prime requisites for this 

 work, aside from the 'hoppers' themselves, are fine wire cages 

 and patience. 



In any case, a study of a collection of individuals living in 

 their normal environment was desirable, for, had such con- 

 ditions first been found in captive stock, one would surely have 

 suspected that these unusual conditions were due to the artificial 

 environment. 



This work has been sufficient, I believe, to show the random 

 segregation of the homologues of all but four (nos. 2, 10, 11 and 

 12) of the first spermatocyte tetrads, and that the recombina- 

 tions found in the group correspond to what would be expected 

 according to the law of chance. 



V. CONCLUSION 



This material clearly presents the following facts: 



1. Constancy of the chromosome complex for the individual. 



2. The occurrence of heteromorphic tetrads in the first sperma- 

 tocyte. 



3. The segregation of these heteromorphic homologues in the 

 first maturation division according to the law of chance. 



4. The formation of the expected classes of second spermato- 

 cytes. 



5. Normal transformation stages for the spermatids. 



6. The occurrence in a group of individuals of practically all 

 possible combinations of the heteromorphic chromosomes. 



These facts taken together may be accounted for by : 



1. The ordinary process of free, chance fertilization acting 

 in a species in which the present forms of the chromosomes 

 which originated through some past reorganization are stable, 

 or: 



2. A reorganization of the complex, involving a change of 

 fiber attachment for each individual before the setting off of the 

 germ cells. 



Both of these possibilities may be tested by breeding: — In the 

 first case parents of known chromosomal constitution would 

 give progeny' with a fixed range of variation — limited by the 



