1 66 ORGANIC EVOLUTION 



The vermiform appendix is less developed in man than 

 in the apes, and in an adult man is relatively smaller than 

 in the human foetus (Plate 96, B\ 



At the inner angle of the human eye is a fold of tissue 

 called the plica semilunaris. This is a remnant of that 

 third eyelid which in many lower vertebrates, notably the 

 birds, is greatly developed and can be drawn over the whole 

 eyeball, inside the outer eyelids (Plate 97). 



These vestigial structures in man have little or no mean- 

 ing until in them we recognize the traces of an earlier con- 

 dition through which our ancestors have passed. 



In human embryology there is every indication that we 

 must regard man as closely related to the rest of the ani- 

 mal kingdom. A little study of the illustrations of the 

 embryos of man and a number of other vertebrates will 

 bring out this resemblance in their embryology, and the 

 fact that the human embryo, in the earlier stages of its 

 growth, has many features which are a reminiscence of its 

 fishlike early ancestors (Plate 98). In the later develop- 

 ment of the human child, after birth, there are .a number 

 of things that are instructive in this connection. In a baby 

 the spinal column has a single curve, as it does in the apes 

 and monkeys, instead of the S-shaped curve seen in the 

 adult human being (Plate 99). The feet are held in a 

 position characteristic of the apes (Plate 100). For a few 

 weeks after birth, the child has a remarkably strong finger- 

 grip, recalling the strength with which the young apes grasp 

 the mother's hair, as she climbs with them among the trees. 

 The young human baby is able to sustain its own weight 

 by its hands, and, when hanging thus, shows often a posi- 

 tion of the legs which is strikingly apelike (Plate 100, B\ 



