BLASTOGENIC VARIATIONS. 167 



Upon members of the Animal Kingdom very few ex- 

 tensive and systematic crossing experiments have been 

 made. The most complete are those of Standfuss,* on 

 various races and species among the Lepidoptera. 

 Standfuss' general conclusion is that on crossing the 

 normal form of a species with a gradually formed local 

 race of the same species, a series of more or less inter- 

 mediate forms results. For example, on crossing Calli- 

 morpha dominula $ with the variety persona 9, the 

 issue resulting were of a very variable form, more or 

 less intermediate, but somewhat more closely resem- 

 bling the type than the variety. In the reciprocal 

 cross, the insects, on the whole, also came nearer to (7. 

 dominula than to the variety, but not so much as be- 

 fore. When species were crossed Standf uss found that 

 the hybrid form lay between the extreme parental 

 forms, but was not strictly intermediate. Arguing 

 from his experiments on crossing various species of 

 Saturnia, Standfuss concludes that the adult offspring 

 are more similar to the male parent than to the female, 

 the extent of approximation depending on the relative 

 age of the two species. Crosses of the male hybrids 

 with the parent forms were in some cases proved to be 

 fertile, and hence there is no reason why such forms 

 should not establish themselves under natural condi- 

 tions. Thus Dr. Dixey, in a very good resume of 

 Standfuss' researches,f says with reference to these hy- 

 brids, " Since the product of this kind of crossing is not 

 found to show a complete reversion to the type of the 

 female parent, it is possible that the existence of vari- 



*" Handbuch der palaartischen Gross-Schmetterlinge," Jena, 1896. 

 t Science Progr., vol. vii. p. 185, 1898. 



