388 THE POPULAR SCIENCE MONTHLY. 



upon children's actions to-day an influence which can be easily 

 discerned, though it may be sometimes obscured. Even such a 

 matter as the elevation of the eyebrows during astonishment may 

 be traced to the desire of prehuman ancestors to erect the hair, in 

 order to make themselves as big as possible, and therefore for- 

 midable to their foes, a habit which animals constantly exhibit 

 when they are suddenly startled. It is the noU-me-iangere prin- 

 ciple, sometimes practiced with good cause, but at other times 

 being the merest " bluff," a veritable trading under false pretenses. 

 It is to this practice of erecting the hair that we owe the invol- 

 untary expression during extreme terror that of the hair stand- 

 ing on end with fright. By disuse we have lost the voluntary 

 power to control the muscles which perform the function of erect- 

 ing the hair ; but the involuntary power still remains. Such 

 seems to be the explanation ; at any rate involuntary erection of 

 the hair during terror is a well-known fact, treated of by Darwin. 

 Enough has been said to show that the characters and habits 

 of children afford every support to the evolutionist ; that what is 

 quite unintelligible and even antagonistic to any idea of special 

 creation becomes significant and full of meaning in the light of 

 the doctrine of gradual development ; that the actions of children 

 when rightly interpreted tell their own tale and may fitly be com- 

 pared to ancient monuments of prehistoric times ; lastly, that the 

 human infant is an interesting object of scientific research, and 

 that even a cross baby should be calmly contemplated by the 

 philosophic mind. Nineteenth Century. 



ANIMAL TINCTUMUTANT8. 



By Dr. JAMES WEIR, Jr. 



THE chromatic function and I use this term to designate the 

 faculty of changing color according to surroundings is pos- 

 sessed by a number of the lower animals. The chameleon is the 

 best known of all the tinctumutants {tinctus, color, and mutare, 

 to change), though many other animals possess this faculty in a 

 very marked degree. In order to understand the manner in 

 which these changes or modifications of color take place, one 

 must know the anatomy of the skin, in which structure these 

 phenomena have their origin. The frog is a tinctumutant, and a 

 microscopic study of its skin will clearly demonstrate the struc- 

 tural and physiological changes that take place in the act of 

 tinctumutation. The skin of a frog consists of two distinct layers. 

 The epidermis or superficial layer is composed of pavement epi- 

 thelium and cylindrical cells. The lower layer, or cutis, is made 



