426 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1912. 



of the medium in which it lives. These experiments have been more 

 than once subjected to scathmg criticism, which is undeserved, as 

 can be demonstrated by an examination of the original sources. 

 By increasing the salinity, Artemia salina passes in several generations 

 nearer and nearer, and eventually completely mto the related species 

 Artemia MuhlJiausenii. On the other hand, by reducing the salmity, 

 it assumes a number of characters which are peculiar to a fresh- 

 water species, the gillfoot (Branchipus, fig. 4, 2). This is most 

 apparent m the gradually emphasized development of the appen- 

 dages and the cihation pending from them! These hairs are at first 

 wanting (la) ; then they appear scattered only on the tip of the ter- 

 minal caudal segment (Ib-d); but finally they surround the entire 

 border as a fringe, having attained an equal length at the same tune 



Among the many experiments which have been made recently upon 

 the lower crustaceans, those conducted by Woltereck upon the long- 

 spined water flea {DapJinia longispina) may be mentioned. In the 

 Untersee, near Lunz Gower Austria), Hves a race in which the head 

 hehnet is low. By feeding these well, in the basin of a hothouse, 

 Woltereck saw them develop into high-helmed forms. If one trans- 

 plants these artificially produced high-helmed races into their former 

 habitat within two years, then all their progeny returns to the low- 

 helmed form. Later offspring, however, remain more high-hehned 

 than the original stock, even when they are returned to normal 

 conditions. Ostwald obtained a similar picture without inheritance 

 in an allied genus, Hyalodaphnia (fig. 5). He placed high-hehned 

 females (laaj, which contained eggs in the broodpouch that were 

 undergoing development, in cold water (0° to 5° C.) and obtained 

 (Ihhj) short-hehned young. Moderately high-helmed gravid females 

 (11 aa), placed in moderately warm water (8° to 18° C), yielded 

 moderately high-helmed young (11&&J, while short-helmed females 

 (lllaaj, placed in warm water (20° C), produced high-hehned young 



I shall now cite a series of examples in which the transmission of 

 an intentionally produced variation in higher plants and animals has 

 been demonstrated. The offspring necessary for these demonstra- 

 tions were produced by the usual bisexual methods — that is, through 

 the fertilization of an ovum; both parents may have been subjected 

 to the change-producing environment, or only one of the parents may 

 have been changed, the other being normal. The nature of the experi- 

 mental variation was as variable as the organism in which it was 

 produced — small and large butterflies, flies, beetles, water and land 

 salamanders, frogs, toads, lizards, chickens, dogs, guinea pigs, rab- 

 bits, rats, and mice. Various kinds of grain and higher flowering 

 plants have yielded positive answers in our experiments: to say 



