R. K. NAB0UR8 169 



germinal iimterial of each species is pure and inviolate from generation 

 to generation, whatever the combinations that are made with them. 

 The fact that two germ plasms come together to make a heterozygote 

 does not alter this situation, because, although combined in fertilization 

 into a harmoniously acting zygotic system, they immediately separate 

 in gametogenesis as though they had not been mixed at all but had 

 been held together only. The resulting soma (the pattern only con- 

 sidered here) indicates that each of the gametes gives the soma 

 characters of its own kind, and that these two sets of characters, from 

 the two parental sources brought together in fertilization, are in a sense 

 dove-tailed one into the other to make the individual heterozygotic 

 combination. 



VII. Conclusion. 



The inheritance behaviour of the colour patterns in these ortho- 

 pterous insects shows clearly the Mendelian type of inheritance, and the 

 essential result of these experiments has been the extension of this 

 principle to a considerable number of types of a phylogenetically low 

 group of ametabolous insects. 



All the hybrid patterns, except a few which have not been 

 adequately examined, show plainly in their visible somatic constitution 

 all the parts which can be distinguished in the somatic make-up of 

 each of their parent patterns. No character of one parent species is 

 ever replaced in the F^ hybrid by any character of the other parent. 

 All the characters of each parent are represented in the F^ hybrid. 

 It follows, then, that these grasshoppers do not exhibit characters, 

 which by crossing can be replaced by other different characters; the 

 whole pattern appears to be the only unit. 



Dimorphism and polymorphism in the length of the wings and pronota 

 are not inheritable, but are somatic, due to variable incident conditions 

 under which the individuals grow. The conditions causing slow growth, 

 extended over several months, produce a preponderance of short winged 

 individuals. These conditions obtain irf the fall and winter, and may 

 be a matter largely of the lack of sunshine. The conditions causing 

 quick growth, extended over a shorter time, produce a preponderance 

 of long winged individuals. These conditions obtain in the spring and 

 early summer and may be largely a matter of an abundance of sunshine. 



I desire to express my thanks to Prof. W. L. Tower for the use of 

 equipment and for much valuable time given in consultation during 

 the progress of the work and the preparation of the MSS. The late 



