MULTIPLE CHROMOSOMES 527 



as the basis for my earlier discussion, although at the time they 

 were not fully identified indi\dduals. Now, with an extensive 

 series secured for me by Miss Carothers, I find that the uni- 

 formity of association, so marked a feature of my early slides, 

 has, for certain chromosomes, given way to an order character- 

 ized by multiples or non-multiples in equal proportions for the 

 individuals studied. For any individual animal however there 

 is no variation. But this species possesses added interest be- 

 cause of associations between euchromosomes to produce octad 

 multiples in which the accessory chromosome does not occur. 

 This is the first unquestionable instance of any such condition 

 in the Acrididae, but its occurrence in a genus of the Locustidae 

 has recently been reported by Miss Woolsey, working under the 

 direction of Robertson. So clear and unequivocal is this con- 

 dition in viridis that its interpretation can not be escaped, and 

 that it should have failed to appear in my early material is 

 most surprising. A careful restudy of my preparations makes 

 it evident that no other multiples than those involving the 

 accessor}^ chromosome are to be found there. In some more re- 

 cently prepared sHdes of earUer lots I was however somewhat 

 chagrined to find individuals with the accessory chromosome free. 

 These various modifications of the complex are most interesting 

 and suggestive and merit extended consideration. 



The following conditions of the first .spermatocyte complex 

 have been encountered so far (plates 1 and 2). 



Class (1 )-12 separate chromosomes = 11 tetrads + the accessory dyad 

 Class (2 )-ll separate chromosomes = 10 tetrads + one hexad 

 Class (3 )-10 separate chromosomes = 8 tetrads + one octad + one hexad 

 Class (4 )- 9 separate chromosomes = 6 tetrads + two octads + one hexad 

 Class (5 )-10 separate chromosomes = 7 tetrads + two octads + one dyad 

 Class (5a)-ll separate chromosomes = 7 tetrads + two octads + one dyad 



and supernumerary 

 Class (6 )-ll separate chromosomes = 9 tetrads + one octad + one dyad 



While the number of chromosomes varies from nine to twelve, 

 the number of chromatids, morphologically recognizable, re- 

 main in all cases forty-six. The particular form of chromosome 

 which I called an 'octad' in my former study ('05) presents 

 itself very conmionly in the new material. 



