58 THE UNIVERSITY OF OKLAHOMA 



osome mechanism ; likewise the behavior of chromosomes in hymen- 

 apteron insects ; and again dominant genes are added evidence that 

 one chromosome is all that is essential for development and sym- 

 metr}^ A monorome organism instead of one with homo'.ogus 

 chromosomes would always breed true for every character. 



The usefulness of bilateral symmetry in nature may be also 

 a reason for its inheritance. Radial symmetry is best suited 

 to sessile anim.als since the- similarity of parts enables them to 

 repel enemies and to obtain food from any direction. Bilateral 

 symmetry is one of the most useful adaptations for swimming 

 organisms such as fishes and the like, for flying and for walking, 

 and for running animals. Tropic responses in animals are condi- 

 tioned by bi'aterality in organisms, such symmetry giving rise to 

 orientation. 



The idea of duplicate genes is becoming more common and 

 there is greater evidence in favor of the fact that duplicate genes 

 may exist in every chromiosome. The result is that the organism 

 is not a mosaic but an organism as a whole.. Symmetry- may be 

 inherited in this way due to multiple factors. 



Mosaics are also added evidence that asymmetrical characters 

 as caused by the genes. Such mosaics may be due to non-disjunc- 

 tion ; chromosome elimination and somatic mutations, and are 

 all accounted for by the chromosome mechanism. 



The first matings of this unilateral character gave in the F^ 

 generation approximately 15 normals to one abnormal, which signi- 

 fies duplicate genes with the character as a recessive. Many of 

 the F.-, selfed gave many families normal with no abnormals. But 

 the ratios added together of abnormals gave an approximate 7:1 

 ratio which agrees with the idea of duplicate genes. 



In certain crosses from the F^ progeny black-spotted, red 

 spoted, red-black, unilateral females and black-red unilateral fe- 

 males, but all males are always non-spotted, for each type. This 

 character, as well as all others so far studied, is sex-limited in its 

 inheritance. 



When a red-black unilateral mother is mated with a black-red 

 non-spotted male, her offspring will be on the average 2 red-black 

 to 1 black-red, with 3 males non-spotted. The ratio is a 2:1 which 

 is a 1:1 and 3:1 Mendelian ratio added together, since one can not 

 determine whether the males are heterozygous or homozygous ; con- 

 sequently the above ratio results. 



The same result is also discovered when a black-red unilateral 

 mother is mated with a non-spotted male from a red-black culture 

 gives approximately ^ families breeding true for this reverse char- 



