356 EwAKT — Variation : Germinal and Environmental. 



scale of a balance, and the four in the other, the four were found to weigh a few 

 grains more than the eight. In tliis case the four foetuses had evidently received 

 the same amount of nourishment as the eight, and were, moreover, able to 

 assimilate all they received. Had these twelve young been born, the eight small 

 ones might, in course of time, have reached the same dimensions as the four large 

 ones.* Very often in a litter of rabbits one or two of the young are small and 

 soon die off, but I once succeeded in rearing a rabbit that, even when nearly six 

 weeks old, was little more than half the weight of the other members of the 

 litter. Eventually the environmental dwarf nearly I'eached the size of its half 

 wild parent, and produced perfectly normal offspring. Sometimes a child is born 

 little more than half the usual weight, owing to deficient nourishment [e.g. to one 

 or more knots in the umbilical cord). Such a child may grow into a man above 

 the average size and have perfectly normal descendants. On three occasions 

 foals from mares ill and out of condition dm-ing the period of gestation proved 

 extremely weak and heli^less. Of the three foals two died during the first year, 

 but the third, though at first a characteristic " weed," is now (as a four-year-old) 

 a fairly presentable animal, and only measures two inches less than his dam. By 

 way of testing the influence of the immediate surroundings during development, 1 

 placed a doe rabbit in a cellar with a north light through which the direct sun's 

 rays never penetrated during winter or spring — a cellar that by its unsanitary 

 condition, and especially by its unsavoury smells, was extremely suggestive of a 

 slum. This doe (after being mated with a half wild buck) was placed in the 

 cellar on the 9th of April, and returned to her hutch on the 8th of May, the day 

 before her young were due. The young only arrived on the 12th May, when, as 

 it happened, I saw them born. There were six in all, two were dead at birth, 

 and the remaining four all died within twent3'-four hours. Since this unhealthy 

 litter the doe has produced thirty-eight young all perfectly normal. Of these, 

 six to the same buck were born after a second sojourn in the cellar ; but during 

 the second stay of four weeks the cellar was in part flooded almost daily with 

 sunshine, and it was, moreover, better ventilated. In the above instance, though 

 plenty of good food was provided, the period of gestation was prolonged, and the 

 vitality of the young enormously reduced. 



It would be a simple matter to give many instances of mammals born with 

 one or more limbs wanting, or otherwise abnormal, owing often to constriction by 

 the umbilical cord. Such " variations," though congenital, are neither inherited 

 nor yet are they transmitted — they are abnormal environmental variations. 



It thus appears that normal variations, during development [i.e. from the 

 conjugation of the germ-cells to the time of hatching or bii'th), are frequently 

 due to an inadequate supply of nourishment. 



* The fcetal rabbits were TvitluD about five days of birth. 



