THE LA W OF LIKENESS, AND ITS WORKING. 221 



moreover, aid in the most valuable manner in connecting 

 facts which otherwise would present a most confusing and 

 straggling array. We may, in truth, sketch in the outlines 

 of the subject in theory, and leave these outlines to be de- 

 leted or intensified by the subsequent progress of knowledge. 

 Buffon speculated, about the middle of last century,, 

 on the causes of heredity, and viewed the subject from a 

 very comprehensive stand-point He assumed that the 

 ultimate parts of living beings existed in the form of certain 

 atoms, which he named " organic molecules," and main- 

 tained that these molecules were received into the body 

 in the shape of food, and became stored up in the various 

 tissues and organs, receiving from each part a corresponding 

 "impression." The molecules in each living body were, 

 in fact, regarded by Buffon as plastic masses, which not 

 only received the imprint, in miniature, of the organ in 

 which they had lodged, but were also fitted to reproduce 

 that organ or part. Potentially, therefore, each molecule 

 might be said to carry within it some special portion of the 

 body of which, for a time, it had formed part. It was 

 organic and, moreover, indestructible. For after itself and 

 its neighbours had been freed from corporeal trammels by 

 the death of the organism in which it had existed, they were 

 regarded as being capable of entering into new combina- 

 tions, and of thus building up afresh the forms of living 

 animals or plants similar to, or widely different from, those 

 in which they had previously been contained. Buffon's 

 theory had special reference to the explanation of cases of 

 the "spontaneous generation" of animalcules in closed 

 vessels, but it also served to explain the cause of heredity. 

 The molecules, each charged with the form of the organ 

 or part in which it existed, were believed ultimately to pass, 

 in the case of the animal, to the egg-producing organs, or, 

 in the plant, to the seed ; the egg and the seed being thus 

 formed, as it were, from materials contributed by the entire 

 body. The germ was to the body at large, as a microcosm 

 is to the greater " cosmos." 



