166 MUTATION 



Here is a plant of characteristic form and flower 

 which regularly produces a small percentage of 

 offspring of strikingly different forms — sparsely 

 branched instead of profusely, with brittle leaves 

 instead of smooth, of stunted size and small flow- 

 ers, with strap-shaped or with ovoidal leaves in 

 place of lanceolate. The unit characters that 

 appear in these peculiar progeny of lamarckiana 

 do not intergrade with the corresponding charac- 

 ters of the parents, and, on self-fertilization, are 

 reproduced in successive generations. 



While the particular kind of mutation exhib- 

 ited by Lamarck's primrose is rare, it is common 

 to find species in which an organ appears, in dif- 

 ferent individuals, in a number of distinct forms 

 constituting the so-called " elementary species " 

 — a term that seems justified since, bred to their 

 like, these forms are reproduced in successive 

 generations. Striking examples of this sort have 

 been found in wild violets by Doctor Ezra Brain- 

 erd, and in the shepherd's purse by Doctors 

 Lotsy and ShuU. Animals have been less care- 

 fully scrutinized for elementary species; but we 

 are not without instances. The true bugs and 

 the straight-winged insects often show both long- 

 winged and short-winged forms, without inter- 

 grades. Some tiger beetles, of both sexes, appear 

 either in a brown or a blue-green dress. Wheeler 

 has collected over a score of pink katydids discov- 

 ered in the United States within recent years, and 

 has noted cases of pink forms of green hemip- 



