THE VEGETABLE AND ANIMAL KINGDOMS. 129 



But the condition of her reproductive system evidently 

 governs the matter of sex, for it is remarked that when her 

 impregnation is delayed beyond the twenty-eighth day of 

 her entire existence, she lays only eggs which become males. 



We have here, it will be admitted, a most remarkable 

 illustration of the principle of development, although in an 

 operation limited to the production of sex only. Let it not 

 be said that the phenomena concerned in the generation of 

 bees may be very different from those concerned in the repro- 

 duction of the higher animals. There is a unity throughout 

 nature which makes the one case an instructive reflection of 

 the other. () 



We shall now see an instance of development operating 

 within the production of what approaches to the character of 

 variety of species. It is fully established that a human family, 

 tribe, or nation, is liable, in the course of generations, to be 

 either advanced from a mean form to a higher one, or degraded 

 from a higher to a lower, by the influence of the physical 

 conditions in which it lives. The coarse features, and other 

 structural peculiarities of the negro race only continue while 

 these people live amidst the circumstances usually associated 

 with barbarism. In a more temperate clime, and higher 

 social state, the face and figure become greatly refined. The 

 few African nations which possess any civilization exhibit 

 forms approaching the European ; and when the same people 

 in the United States of America have enjoyed a within-door 

 life for several generations, they assimilate to the whites 

 amongst whom they live. On the other hand, there are 

 authentic instances of a people originally well-formed and 

 good-looking, being brought, by imperfect diet and a variety 

 of physical hardships, to a meaner form. It is remarkable 

 that prominence of the jaws, a recession and diminution of 

 the cranium, and an elongation and attenuation of the limbs, 

 are peculiarities always produced by these miserable condi- 

 tions, for they indicate an unequivocal retrogression towards 

 the type of the lower animals. Thus we see nature alike 

 willing to go back and to go forward. Both effects are simply 



