ii LIVING MATTER 49 



a teleological principle, regulating the transmutation and adapt- 

 ability of the new organ, a principle in sharp contrast with the 

 canons of the materialistic doctrine, which seeks for the mechanical 

 causes of phenomena, and excludes all mystical, transcendental 

 interpretations. The neo-Larnarckians renounce the teleological 

 principle, on the strength of recently acquired data as to the 

 determining action of certain external agents, e.g. light, heat, 

 water, gravity, chemical substances, action of parasites, mechanical 

 action (photomorphosis, thermomorphosis, hydromorphosis, geomor- 

 phosis, chemornorphosis, biomorphosis, mechanomorphosis, etc.). 

 This field of research, as cultivated especially by the modern 

 botanist, is one of the most fruitful to the progress of biological 

 science. 



At the same time it must be remembered that the external 

 agent, e.g. light or heat, which determines a modification in 

 the structure and conformation of an organ, is not the true cause 

 of such a modification, but is rather the external stimulus adapted 

 to develop a variation which already existed potentially in that 

 organ. The determining agent, therefore, creates nothing new, it 

 only stimulates the species to the expression of those properties 

 which it already possesses potentially. This conclusion, which is 

 inevitable in the present state of our knowledge, must obviously 

 limit to a great extent (some even say reduce to zero) the value of 

 the direct action of external agents in the formation and trans- 

 formation of species. 



But further : in order that the influence of the environment in 

 the production of new characters in a species shall be efficacious- 

 and enduring, it is necessary to presuppose that the newly acquired 

 characters are hereditary. Does any such heredity really exist ? 



This is one of the problems most keenly discussed among 

 modern biologists. It is obvious that a decidedly negative reply 

 would cause the whole edifice of the Lamarckian and neo- 

 Lamarckian theory to crumble. But no one is yet in a position 

 to give a definite answer. The majority of the facts that were at 

 one time cited in proof of the heredity of acquired characters have 

 been triumphantly refuted by Weismann. Some few data relating 

 to the lower organisms (Bacteria and Saccharomyces) remain, in 

 which the heredity of newly acquired characters seems to be de- 

 monstrated ; but how far these data are of value in the solution 

 of the general problem with which modern biologists are so 

 engrossed, is a matter for discussion. 



For the present it must be confessed that with the exception of 

 these few cases among the inferior organisms, all the attempts 

 hitherto made to obtain new forms of plants and animals by the 

 effect of one or several external causes have given negative results. 



IV. Starting from a profound criticism of Darwinism and 

 Lamarckism, Nageli (1887) founded a new theory of evolution, 



VOL. i E 



