1889.] «^45 [llyder. 



series of lateral pairs, capable of effect in <? only one movement, which is 

 itself the expression of an adjustment which it is imjiossible to prove first 

 arose in any other way than as the result of obtaining the greatest phy- 

 sical effect in moving the body most efficiently through the water with 

 only one kind of recurring and alternating muscular contractions happen- 

 ing on opposite sides of the bod}\ Just here the natural selectionist jumps 

 to his feet and declares, "There, you have granted all that we claim." 

 But not so fast ; wait a moment. It is competent for him totirst prove that 

 this simple muscular training does not increase or stimulate the develop- 

 ment of muscle through further histological and morphological differentia- 

 tion and cell-multiplication, and the subsequent inheritance of this acquired 

 complication and increased strength through use. Since there has not yet 

 been offered an iota of conclusive evidence to the contrary, and, since the 

 necessary investigations have not yet been made to disprove my position, 

 I insist upon remaining an absolutel}^ orthodox Lamarckian. 



There are still other reasons for taking the above-stated position, which 

 cannot now be referred to except brief!}', as they arise from a considera- 

 tion of the far more intricate and difficult question of sexuality. The 

 greater part of the recent discussions of the significance and origin of 

 sexuality are so transcendental in their character as to promise little of 

 permanent value, since all of the hypotheses yet propounded, with the 

 exception of the two radically different views propounded by Patrick 

 Geddes and myself, overlook the importance and necessit}^ of keeping in 

 sight the general ph3'sical doctrine of the conservation of energy. No 

 biologist has yet recognized with sufficient clearness the overwhelming 

 importance of the principle of overnutrition, which was at once the cause 

 of sexuality, the struggle for existence and the direct means of the evolu- 

 tion of all larval forms. Overnutrition, resulting in sexualitj', was the 

 means of heaping up potential physiological energy in the egg so as to 

 render larval development and a larval struggle for existence a possibility ; 

 and any other view of the origin of all or most larval types has little or 

 no scientific warrant in fact. If, therefore, physiological energy was 

 superimposed upon physiological energy or potentially stored, so to 

 speak, in a germ-cell of exaggerated dimensions, it follows that the main- 

 spring of evolution or'its motive force is to be sought in sexuality and not 

 in the Weismannian speculations as to the significance of one or two polar 

 cells or the existence of a hypothetical germ-plasma which amounts in 

 essence only to a restatement of the fact of heredity to which a hypo- 

 thetical-physical basis is thus assigned. Since it can be proved that larval 

 adaptations have occurred independently and wholly regardless of the 

 attained differentiation of the parent, the fallacy of Weismann's doctrine 

 of the immortality of the germ-plasma must be sufficiently obvious to those 

 who have followed him in the development of his extraordinary errors. 



I wish it to be distinctly understood that I do not consider all evolution 

 as mechanical, but I do wish to be understood that the processes of evo- 

 lution are physical and must ultimately be treated as physical problems. 



PROC. AMER. PHILOS. SOC. VOL. XXVI, 130. 3q. PRINTED DEC. 12, 1889. 



