II. 



Biological Theories. 



I.— THE NATURE OF HEREDITY. 



THE numerous extant theories of heredity all begin with the 

 assumption that some characters are transmitted from parent 

 to offspring, while they differ as to the " transmissibility " of certain 

 others. In the case of characters which they all assume to be trans- 

 mitted, they differ largely as to the mechanism of the transmission. 

 Haeckel holds, or at any rate did hold, that the medium of transmis- 

 sion, the carrier of the influence which produced new characters like 

 the old ones, was a kind of molecular movement. Darwin imagined 

 certain particles derived from all parts of the body to serve the same 

 function. Both agreed as to the transmission of some " acquired " 

 characters. Weismann opposes both these views and relies upon a 

 supposed continuity of germ-plasm for the explanation of the trans- 

 mission of all except "acquired" characters, and of these last he 

 denies the transmissibility. The other theories which are held by 

 modern biologists are all more or less similar to one or other of these 

 two last — some rely upon continuity of something or other, the rest 

 upon the transmission of material particles derived from various 

 parts of parental and ancestral bodies. 



I do not propose to weigh afresh the relative claims of these two 

 schools of theorists, nor to ally myself with either school by producing 

 a new theory in conformity with its fundamental principles. Both 

 schools appear to me to be equally wrong, and to have set out with 

 equally false notions as to the nature of the phenomenon they have 

 attempted to explain. 



The phenomenon I propose to explain is the relative constancy 

 of specific form in several generations of any species of animal or 

 plant, i.e., the reappearance of certain characters in many individuals 

 belonging to several generations. It is not a transmission of 

 characters from parent to offspring alone, not only the reproduction 

 in the offspring of characters possessed by the parents or more remote 

 ancestors ; and this will be shown by the first example I shall bring 

 forward in illustration of my view. 



In each successive generation of termites or " white ants," are 

 found certain individuals, called " soldiers," which are blind and 

 wingless, and which are incapable of any reproductive function. 

 They have enormous heads, much larger than any of the other 



