1915] 



MACDOUGAL MODIFICATION OF GERM-PLASM 255 



laboratory conditions in which both the nature of the reaction 

 and the identity of the inciting agent may be found. The most 

 notable series of experiments of this character which have as 

 yet been carried out are those of Tower with the potato 



beetles. 



Over two hundred species of seed-plants selected for their 

 suitability and promise of response have been taken into the 

 series of cultures of the Department of Botanical Eesearch 

 on mountain top, desert, and at the sea-shore, less than eighty 

 of which have survived and about a score continue in all three 

 locations. The most notable feature in the behavior of these 

 plants put under stress in unaccustomed habitats consists in 

 divergences in sexual reproduction and seed-formation. Con- 

 jointly with this decrease of the sexual reproduction, vegeta- 

 tive propagation assumes a greater importance. Shoots are 

 variously affected. The measurement of these departures 

 and their fate when the nth. generation is returned to the 

 original habitat, or to a place in which the habital tension is 

 changed, will be necessary to determine whether or not perma- 

 nent impress on the species has been made. 



The second method would include all forms of experimenta- 

 tion in which inciting agents would be applied directly to the 

 reproductive bodies, in which case any deviation from the 

 usual or typical would be more clearly attributable to changes 

 in the germ-plasm. 



It is pertinent to call attention to the necessity for new 

 viewpoints and new standards in the evaluation of any results 

 which may be obtained in such manner. We are not likely to 

 go far or progress easily into the region of the unknown if 

 we attempt to interpret these effects too directly, with the idea 

 that determiners, inhibitors, genes, etc., are ultimate or even 

 penultimate units. In brief, the time has come for testing the 

 performances of lineal series of organisms by methods in 

 which attention will be centered upon the physico-chemical 

 complex and an open eye will be kept for cleavage lines which 

 may cut across directly or obliquely the limits of all of the 

 arbitrary concepts of alternate inheritance. The house of the 

 living thing is inclusive of walls, doors, roofs, windows, floors, 



