SEGREGATION OF HOMOLOGOUS CHROMOSOMES 453 



Several important questions at once present themselves. 1) 

 Since these heteromorphic but homologous dyads segregate in 

 the first maturation division, what is their distribution in rela- 

 tion to the accessory (that is, to sex)? 2) As it is obvious that 

 at least sixteen sorts of spermatozoa are formed in these two in- 

 dividuals, would the well known constancy of the complex — as 

 shown by numerous workers on Orthoptera — hold for this 

 species or would a large number of individuals give all possible 

 combinations? Or would certain combinations result and others 

 fail? 3) Would the somatic complex of the female be constant? 

 (Using this as an index of the oogonial complex) . 4) If the com- 

 plex is constant for the species, what is the mechanism by which 

 it is regulated? Is there selective fertilization of a most com- 

 plex sort, or is there free fertilization with regulation occurring 

 at the time of the maturation of the egg? (Since copulation 

 occurs some twenty-four hours before the polar bodies are 

 formed the latter seemed quite possible.) 



The first of these questions was a matter to be determined by 

 a study of a given individual and was at once worked out from 

 the material in hand. The others required a considerable num- 

 ber of individuals and it was largely for the purpose of obtain- 

 ing these that a collecting trip through the southern and western 

 states was undertaken during the summer of 1915. 



For a determination of the method of segregation of the hetero- 

 morphic homologues in relation to the accessory, one hundred 

 camera lucida drawings of entire complexes were made at ran- 

 dom. As stated above, the two individuals in the collection 

 were alike; fifty-seven of the drawings were from one individual 

 and forty-three from the other. Plate 1 is based on only one 

 individual, however, but is representative of both. 



These drawings are from sections. The chromosomes from 

 one cell are always in two and sometimes three sections. The 

 sections were all present, in order and in straight rows, so that 

 the problem of identifying in successive sections these large 

 clear cells with sharply formed spindles is much simpler than it 

 may appear to those accustomed to less favorable material. 

 The chromosomes were first outlined under the camera lucida 



