48 EVOLUTION 



vivals " persist in the recesses of all manner 

 of venerable institutions. 



From this point of view our own body is a 

 veritable museum of relics. But these are 

 not all equally venerable. In the first place, 

 there are antique structures which are present 

 only in the embryo, not normally coming to 

 anything in the adult, as is the case with all 

 the visceral clefts (or gill-clefts) except the 

 first, which survives as the Eustachian tube. 

 In the second place, there are old-fashioned 

 structures which persist in adult life, but in 

 much disguised form. Thus the gill-arches, 

 whose primary significance (in the lower Verte- 

 brates) was to support gills, persist in our body, 

 almost unrecognizably transformed, in the 

 skeletal support of the tongue and in the 

 framework of the larynx. In the third 

 place, there are vestigial structures in a 

 stricter sense, because far more recent 

 dwindling residues persistent in adult life, 

 but either functionless or relatively unim- 

 portant, such as the minute " third eyelid " 

 which lies in the median angle of our eye, or 

 the muscles of the ear, which in occasional 

 individuals are strong enough to move the 

 trumpet, or the vermiform appendix on the 

 large intestine. This last anachronism seems 

 not merely to have outlived its usefulness; it 



