SEGREGATION OF HOMOLOGOUS CHROMOSOMES 457 



homologues ; e.g., tetrads with two atelomitic dyads and tetrads 

 with two telomitic dyads as well as J-shaped tetrads. The only 

 way to demonstrate that such recombination occurs is through 

 breeding experiments. But since I have collected at random a 

 considerable number of individuals (eighty-two) and have ana- 

 lyzed their first spermatocyte complexes, and have found the 

 types of chromosomes which would be expected from the above 

 assumptions, I have ventured to use the term recombination to 

 express the relationship of those different types to each other. 



It is obvious from the above section, that the two indi- 

 viduals there considered formed sixteen sorts of spermatozoa, 

 so far as the selected elements are concerned. A study of a com- 

 paratively large number of animals was undertaken for the pur- 

 pose of finding, in the first place, whether or not the complex is 

 constant for the species and, secondly, if not, to determine the 

 range of variation. The results from sixty-two individuals are 

 given in plates 2 to 9. The chromosomes on these plates are 

 arranged in the same manner as on plate 1, except that only 

 one complex from an individual is shown ; therefore each of the 

 horizontal rows represents one animal. There are two exceptions 

 to this statement: number 32a' is a spermatogonial metaphase 

 from the same individual as number 32, and number 63a' is a 

 spermatogonial metaphase from animal number 63. 



It will be seen from plate 1 that animal number 1 has, as 

 already stated, in addition to the three J-shaped tetrads, four 

 atelomitic and four telomitic chromosomes. Such a complex 

 was found to be constant for two individuals. This statement 

 is based on one hundred camera lucida drawings. Only one com- 

 plex is shown from the succeeding animals, but a comparative 

 study of a number of complexes was made in each case so that 

 it can be safely stated that the complex is practically constant 

 in any one individual. 



Taking up animal number 2 (plate 2), we find five atelomitic 

 tetrads, numbers 7, 9, 10, 11 and 12; one heteromorphic tetrad, 

 number 1; and the remaining five telomitic. Passing on to ani- 

 mal number 3 we find six atelomitic, three heteromorphic (J- 

 shaped) and onfy two telomitic tetrads. Chromosome number 1 



