WEISMANNISM AND ENT05I0L0GY. 45 



supported by so large a consensus of opinion as to be termed a 

 " natural law," it still retains its subjectivity to man, and remains, as 

 Professor Karl Pearson puts it, " only a shorthand method of resuming 

 a wide field of sense impressions in one short formula," in other 

 words, a labour-saving appliance for the economy of thought. 



Those who have read the modest, yet outspoken preface to 

 Germinal Selection will bear me out in saying that Professor Weismann 

 is perfectly conversant with the limitation of theories in general, and 

 his own in particular, in this direction, and does not hold the exag- 

 gerated notions of their permanence and objectivity that some of his 

 critics would appear to do. It has been urged as an objection to 

 Weismann 's theory of the " germ plasm," that he found it necessary 

 to meet the attacks of his critics by a modification of the absolute 

 unalterability of the germ plasm and the addition of the so-called 

 new theory of " germinal selection." I have never been able to find 

 that the absolute unalterability of the germinal substance was stated 

 in The Germ L'lasin, possibly it was so stated in one of his earlier essays 

 that I have not seen, but, when reading The Germ Plasm, it appeared 

 to me that it was taken as an accepted principle, if not explicitly stated, 

 that the germ substance must increase and multiply through the 

 assimilation of nutriment supplied by the soma or body which also 

 forms its environment. Modification by the quality of the nutriment 

 and the temperature and pressure of the surrounding soma would of 

 course be not only possible but probable, but Weismann's view was 

 that the germ plasm was unalterable, and had absolute immunity 

 from any direct interference by, or inheritance from, the body as 

 opposed to Darwin's "pangenesis." 



In any case I cannot see how modifications or additions to the theory 

 as first stated can be brought forward as objections to the theory as at 

 present constituted ; surely it must stand or fall on its present merits or 

 demerits. It is surely rather a justification of the early publication of 

 this theory that the wide-spread criticism to which it was at once 

 subjected enabled its author to remedy its weakness by alteration and 

 the addition of what is, strictly speaking, not a new theory but a further 

 extension of the older theory of natural selection — as necessary to 

 Weismann's Theonj of the yerni plasm as the acceptance of some 

 scheme of heredity was to the Orit/in of species bij natural selection. 

 Just as we apply natural selection upwards from the struggle 

 among individuals to the struggle of species and genera, or 

 wuth man to the struggle of tribes, communities, or nations, 

 with each other ; so we may, Avith equal justice, apply it down- 

 wards to the struggle of the different parts or organs of a develop- 

 ing embryo (the " intra- selection " of George Eomanes) and the 

 "struggle of the ultimate living units " of which, according to Weis- 

 mann, the germinal substance is theoretically composed. This last is 

 "germinal selection," and if we accept " natural selection " in any 

 form, we can only legitimately attack this theory by rejecting the sub- 

 division of the germinal substance into separate living units. Weis- 

 mann's assumption of ultimate units and their elaboration into 

 organised groups or aggregations, units of higher order or " determi- 

 nants " as he calls them, is, of course, equally as theoretical as the 

 assumption of atoms and molecules by the physicist, and has the same 

 justification. Unless we assume some subdivision of the germinal 



