May 31, 1895.] 



SCIENCE. 



(jdl 



tiou of his hypothesis of inheritauce. Its 

 extreme elaboration is its greatest weakness, 

 and in it, no less than in all preceding hypo- 

 theses, the theory of a separate category of 

 particles carrying hereditary potentialities 

 again appears. 



The one criticism that holds of all tliese 

 hypotheses is that they are one-sided and 

 ignore a most important set of factors in in- 

 heritance, namely, the purely statical ones, 

 or those arising from the mere physical 

 properties of the living matter of the germ 

 viewed as if it were a dead, inert mass, sub- 

 ject to the operation of the reciprocal at- 

 traction for one another of its constituent 

 particles. All of these bj'potheses, more- 

 over, assume that it is only wme of the mat- 

 ter of the germ that is concerned in the 

 process of heretlitary transmission, and that 

 the remainder may be regarded as passive. 

 The entire germ, on the contrary, or all of 

 it that undergoes development, must be 

 considered as a single whole, made up of a 

 va.st number of molecules built up into a 

 mechanism. Such a molecular mechanism, 

 it must be supposed, cannot set free the po- 

 tential energy of its parts except in a cer- 

 tain determinate order and way, within 

 certain limits, in virtue of the initial phj'S- 

 ical structure of the whole. If the germ is 

 free to do that, as must happen under 

 proper conditions, as a mechanism, its parts, 

 as they are thus formed by their own metab- 

 olism, it may be assumed, will inevitably 

 and nearly recapitulate the ancestral devel- 

 opment or that typical of the species. It 

 must do this as a mere dynamical system 

 or mechanism, the condition of which at 

 one phase determines that of the next, and 

 so on, to the completion of development. 



In the present state of our knowledge we 

 are not prepared to frame a purely mechan- 

 ical hypothesis of inheritauce that shall an- 

 swer every requirement, in spite of the fact 

 that no other is possible. Herbert Spencer 

 and Professor Haeckel long ago pointed out 



that such au hypothesis is a necessity grow- 

 ing out of the very requirements that must 

 be satisfied in any attempt to coordinate 

 the phenomena of biologj' with those of the 

 not-living world. The material basis of 

 life is always a chemically and mechanically 

 compounded substance. To the very last 

 molecule, such a body must betraj- evidence 

 of arrangement or structure of its parts that 

 should make it a mechanism of the utmost 

 complexity and requisite potentiality as a 

 transformer of energy through the mere 

 transposition and rearrangement of such 

 parts. "We find indeed that living matter 

 is chemically the most complex and unsta- 

 ble substance known. It is composed 

 largely of carbon, a quadrivalent element 

 that stands alone in its power to combine 

 with itself and at the same time hold in 

 chemical bondage groups of atoms repre- 

 senting other chemical bodies. Such groups 

 are probablj' held together in great num- 

 bers metamerically by the reciprocal or 

 otherwise unsatisfied affinities of the large 

 number of carbon atoms entering into the 

 composition of the proteid molecule. In 

 this way the massive and structurally com- 

 plex molecule of protoplasm may be sup- 

 posed to have arisen. We may thus trace 

 the genesis of the peculiarities of living 

 matter to this singular property of the car- 

 Ijon atom. On such a Ijasis we may sup- 

 pose that the ultimate molecular units are 

 identical with the physiological units, so 

 that their structures may not only deter- 

 mine the nature of the metaljolism they can 

 undergo, but also be the ultimate units of 

 form or morphological character. 



What especially gives color to these sus- 

 picious is the extraordiuaiy variety of 

 changes, alteration of properties or powei-s, 

 and the vast variety of living matter, as 

 represented by the million or more of known 

 distinct living species of organisms. It is 

 as if the permutations, transformations, and 

 the dvnamical readjustment of the meta- 



