Inheritance of Habitat Effects. 55 



this point. There are, however, a number of records of the ap- 

 pearance of definite qualities or morphological characters in 

 the yeasts, which were transmissible and permanent. These 

 departures were not so striking as to be capable of being regarded 

 as mutational, and their origin has been ascribed to the influence 

 of the environment by experimenters of notable skill, such as 

 Beijerinck, Winogradsky, Lepeschkin, Hansen, and Barber. 

 It may be recalled in this connection that environic responses 

 are generallv sudden, and that the entire range of departure may 

 be made in a single generation, at most in two or three. 



The recently published work of Pringsheim constitutes one 

 of the most notable contributions to our knowledge of variability 

 among lower organisms. This author, after a comprehensive 

 review of his own work and of other available evidence obtained 

 by a study of accommodations or adaptations of yeasts and 

 bacteria to unusual temperatures, culture media, and poisons, 

 concludes that some of these variations are fixed and trans- 

 missible both asexually and by spores, while others are not. 

 It is important to note that the alterations concerned are direct 

 functional responses to the environment. 



My own earlier work with relation to this subject consisted 

 chiefly of ovarial treatments in which the main and accessory 

 reproductive elements of seed-plants were subjected to the direct 

 action of solutions of various kinds. New combinations of char- 

 acters constituting a distinct elementary species or genotype 

 were obtained in one plant, and the divergent type has been 

 found to transmit its qualities in the fullest degree as far as tested 

 to the fifth generation. Still more marked forms were obtained 

 in a second genus, the divergent progeny being lost in transfer- 

 ence to the Desert Laboratory, while marked responses have been 

 obtained in the extensions of these experiments upon species 

 representing widely different morphological types in Arizona. 

 The greater majority of the tests have been made upon plants 

 growing under natural conditions, so that environmental reaction 

 in addition to that of the specific reagents, might be excluded. 

 Progenies representing many species, including thousands of 

 individuals, many of which are divergent, are now under obser- 

 vation. Absolute finality of decision with respect to the stand- 

 ing of the new types may be reached but slowly. 



