328 C. E. MCCLUNG. 



previously expressed regarding these matters. Just now I wish 

 to consider the bearing that the peculiar multiple chromosomes 

 of Hesperotettix, Mermiria, Chortopliaga and Anabnis have upon 

 the general questions of heredity raised by the experimental 

 work of the Mendelian school and by de Vries and his followers. 



2. The Chromosomes and Mendel's Laius. 



The first attempt to establish a correlation between cytological 

 phenomena and the operation of Mendel's laws was made by 

 Sutton in 1903, and was based upon Orthopteran material pre- 

 pared and studied to a large extent in my laboratory. It was in 

 thorough concordance with the laboratory results and represented 

 the final step in the establishment of the theory of the individuality 

 of the chromosomes and their relation to body characters. Done 

 independently of Montgomery, it yet had as its fundamental idea 

 the belief that half the chromosomes are paternal and half maternal, 

 and that at the time of numerical reduction there is a union of 

 homologous chromosomes in pairs. Montgomery clearly stated 

 this idea of the union of parental chromosomes and should have 

 due credit for it, but it is to Sutton's work that we are indebted 

 for the detailed evidence of this fact, and for its theoretical appli- 

 cation to the appearance of alternative characters in normal and 

 hybrid breedings. It is this idea of definite association between 

 chromosomes and characters and the explanation it offers for the 

 purity of the germ cells and the recession of traits that renders 

 the work of Sutton unique aad makes it valuable. 



There is no necessity for entering into any extended discussion 

 of Sutton's results because, coming opportunely as they did with 

 the renaissance of Mendel's conceptions, they immediately gained 

 attention and are generally well understood. The essential fea- 

 ture of his conclusions is that there are in the somatic and im- 

 mature germ cells a double series of chromosomes, one derived 

 from the father and one from the mother. In synapsis this double 

 series is united into one by the pairwise fusion of homologous 

 chromosomes which remain in this state until the reduction divi- 

 sion when they are separated again into a series which is of neither 

 purely maternal nor paternal origin. This is offered as an expla- 

 nation of the purity of the germ cells postulated by Mendel. 



