THE LAW OF LIKENESS, AND ITS WORKING. 



557 



and six toes on each hand and foot. Salvator's 

 family likewise consisted of four children, three 

 of whom possessed the six fingers and six toes of 

 their father and grandparent ; the fourth and 

 youngest possessing the ordinary number of di- 

 gits. The four mothers of the second generation 

 of Kelleias exhibited no abnormality in respect 

 of hands or feet, and hence the hereditary influ- 

 ence of the female parent doubtless made itself 

 felt in the development of a proportion of normal 

 haudsand feet — although, as far as the genealogy 

 of the family is traced, the proportion of six- 

 fingered and six-toed members clearly tends to 

 exceed that of those possessing the normal num- 

 ber of fingers and toes. 



Having thus selected and marshaled some of 

 the chief facts relating to the occurrence of hered- 

 ity or the likeness between parent and offspring, 

 it may be fairly urged that these facts seem to 

 establish the existence of some well-defined law, 

 in virtue of which the bodily structure, the mental 

 characteristics, or even the peculiarities induced 

 by disease, are transmitted from one generation 

 to another. And it also becomes an important 

 study to determine the causes which operate in 

 producing such variations in the law of inheri- 

 tance as we have endeavored to illustrate in the 

 case of certain groups of lower animals. Can we, 

 in other words, account for the similarities and. 

 resemblances, and for the diversities and varia- 

 tions, which living beings present, apparently as 

 a natural sequence of their life, and of the opera- 

 tion of the laws which regulate that existence ? 

 The answer to some such question as the preced- 

 ing closely engaged the attention of physiologists 

 in former years, the result of their considerations 

 being the framing of various theories whereby 

 the facts of heredity could be correlated and ex- 

 plained. It is evident that any explanation of 

 heredity must partake of the nature of a mere 

 speculation, from our sheer inability to penetrate 

 deeper into the investigation of its laws than the 

 observation of phenomena can lead us. But, 

 when rightly employed, generalizations and theo- 

 ries serve as leading-strings to the truth ; and, 

 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 deleted or 

 intensified by the subsequent progress of knowl- 

 edge. 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 tact, 

 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. Poten- 

 tially, 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 neighbors had been freed from cor- 

 poreal trammels by the death of the organism in 

 which it had existed, they were regarded as being 

 capable of entering into new combinations, 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 be- 

 lieved ultimately to pass, in the case of the ani- 

 mal, 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 contrib- 

 uted by the entire body. The germ was to the 

 body at large, as a microcosm is to the greater 

 " cosmos." 



A second authority who framed an explana- 

 tion of the causes of likeness was Bonnet, who 

 maintained that lost parts were reproduced by 

 germs contained in the nearest portions of the 

 injured body ; while, by his theory of emboite- 

 ment, it was held that each germ was in itself the 

 repository of countless other germs, these bodies 

 being stored up in a quantity sufficient for the 

 reproductive needs of countless generations. 

 Prof. Owen's explanation depends upon the 

 recognition of the fact that certain of the cells 

 of the germ from which the living being springs 

 pass into its body, and there remain to transmit 

 to its successors the material characters which it 

 has acquired ; while, also, the repair of injuries, 

 and the propagation of new beings by budding 

 and like processes, are explained on the supposi- 

 tion that these germ-cells may grow, increase, and 

 operate within the organism which they are ulti- 

 mately destined to propagate. Lastly, Mr. Dar- 



