VARIATIONS, DUE TO REVERSION. 95 



the right and left sides are extremely unequal; the 

 far greater number of species are dextral, with rare 

 and occasional reversals of development, and some 

 few are normally sinistral; but, certain species of 

 Bulimus, and many Achitinellae, are as often sinis- 

 tral as dextral. I will give an analogous case in 

 the great articulate kingdom: the two sides of Ve- 

 rucca are so wonderfully unlike, that without careful 

 dissection, it is extremely difficult to recognize the 

 corresponding parts on the opposite sides of the 

 body; yet it is apparently a mere matter of chance, 

 whether it be the right or the left side that under- 

 goes so singular an amount of change. One plant is 

 known to me, in which the flower, according as it 

 stands on the one or other side of the spike, is un- 

 equally developed. In all the foregoing cases, the 

 two sides of the animal are perfectly symmetrical at 

 an early period of growth. Now, whenever a species 

 is as liable to be unequally developed on the one side, 

 as on the other side, we may infer that the capacity for 

 such development is present, though latent, in the un- 

 developed side. And as a reversal of development 

 occasionally occurs in animals of many kinds, this 

 latent capacity is probably very common." 



After citing a multitude of instances, showing past 

 degeneration; that characters may long lie latent in 

 the individuals of the species ; and the capacity, of such 

 individuals, to regain such characters, whenever the 

 conditions of their development are restored to them ; 

 he says : 



" From these several facts, it must be admitted, that 

 certain characters, capacities, and instincts, may lie 

 latent, in an individual, and even in a succession of 

 individuals, without our being able to detect the least 

 signs of their presence." 



