new movement of advantage in the life race. Its tendency to 

 hereditary transmission must be as great as that of an extra fin- 

 ger, while it would escape the checking influence of the race 



It is equally possible that an extreme development, or an im- 

 portant duplication of brain tissue, might appear. Slight deficiency 

 or excess of brain tissue is often transmitted through several 

 generations. The former is in the line of reversion towards an 

 ancestral type, or towards some new degraded type, in which 

 organs belonging to several types may exist in combination. The 

 latter is in the line of development of a new type. Extreme 

 variations in this respect are, of course, exceedingly unlikely to 

 be transmitted. But minor variations are frequently transmitted, 

 and it is impossible to say where the line must be drawn. It is 

 quite possible that considerable anomalies may be occasionally 

 transmitted to descendants. An animal might appear with an 

 excessive brain development, or some brain duplication, yet this 

 not be sufficient to destroy the due balance of the organs, or 

 prevent sexual fertilization. And if such an excess were trans- 

 mitted through several generations, the animals possessing it 

 might, through superior mental ability, crowd out and replace 

 their less able kindred. Possibly in this manner the long reach 

 upward, from ape to man, might be made almost in a single step. 



In organic, as in inorganic nature, there are dividing lines, on 

 opposite sides of which weights tend to fall in opposite direc- 

 tions ; or water-sheds, which divert the flow of waters to oppo- 

 site oceans. An animal species may be exactly adapted to sur- 

 rounding conditions; but a scion of this species may arise not 

 fully adapted to the environment, and it may transmit its anoma- 

 lous organization through several generations. If the anomaly 

 be a marked one, a struggle is at once set up within the organ- 

 ism. The organic formation of the animal may not be out of 



decidedly advantageous one. Two tendencies exist within the 

 animal, the tendency to conform to the hereditary habits of its 

 type, and the tendency to avail itself of its new powers. There is a 

 struggle between instinct and reason. Some divergence of habits 

 will be very likely to arise, but not so great as there would be 

 were there no instinctive pull towards the normal habits. If the 

 anomaly be transmitted to offspring, the newly gained habits will 



