23.2 Heredity and Eugenics 



asexual reproduction. In animals a considerable array of 

 domesticated forms are definitely the product of hybridiza- 

 tion. Poultry, for example, are derived from two or three 

 original stocks which have been intercrossed numberless 

 times, and from these crosses have resulted variations in 

 the arrangement of the parental characters and combina- 

 tions of characters. The same is true of domesticated 

 pigeons, where hybridization has been carried out to a very 

 great extent, and in dogs, cats, mice, rabbits, rats, guinea- 

 pigs, swine, and in practically all domesticated organisms 

 essentially the same condition exists. Unfortunately, in 

 domesticated organisms the beginning of these modi- 

 fications is shrouded in antiquity, and while man has 

 reared dogs, swine, pigeons, and poultry for a long period, 

 and while there have arisen under his hand the variations 

 which are now seen under domestication, the manner of 

 origin is unknown, and the best that can be done is to 

 make plausible guesses as to what the procedure really was. 



The modification of both wild and domesticated stocks 

 through hybridization is well known to all students of 

 hybridization, and these modifications are of two general 

 categories: First, the production of new combinations of 

 existing attributes, and second, the origin of de novo varia- 

 tions based upon the attributes of the crossed stocks. The 

 first is by far the most common change, and the second 

 is relatively rare in occurrence. I may illustrate the 

 results produced in these two kinds of modifications by 

 crossing, by examples taken from my cultures. 



L. signaticollis has in the full-grown larvae one row of 

 black spots on the dorsal side, with a deep chrome-yellow 

 body color, and in the adult the elytra "are marked with 

 irregular rows of impressed punctations with a deposit of 



