20 STUDIES IN LIFE AND SENSE. 



the development of the structures just described, must be regarded 

 as an occurrence of the most natural description. In such animals 

 also as the frogs, which breathe by gills in early life, or those curious 

 efts, the Proteus and its neighbours, which breathe by gills through- 

 out life and develop lungs in addition, the appearance of gill clefts 

 and arches in their early existence must be regarded as a perfectly 

 normal and natural feature. Here, however, the apparently regular 

 course of gill development ends. For, when we ascend to the three 

 highest classes of vertebrate animals reptiles, birds, and mammals 

 we discover that lungs, and lungs alone, form the breathing organs 

 of these groups ; gills having no share whatever in their respiration. 

 Yet the puzzle of life waxes apparently intricate enough in its details, 

 when we discover that in the early life of each reptile, bird, quad- 

 ruped, and man, the gill clefts appear with as unfailing regularity as in 

 the gill-breathing fish or frog. Whatever may be their ultimate fate, 

 it is, at least, certain, that the gill clefts and arches of humanity are 

 a veritable possession of our early life. Their further history is 

 simply one of obliteration, united with a degree of modification in 

 which they become elaborated into structures useful to higher life, 

 but unknown, of course, in the lower tribes which retain their gill 

 arches as supports for their gills. We find that the first of these gill 

 clefts becomes converted into part of the ear structures. The outer 

 canal of the ear, the " drum," and the Eustachian tube which places 

 ear and throat in communication, represent the modified first gill 

 cleft of our early life. As has been remarked, it is a curious fact of 

 human development that the foregoing parts in the ear of man repre- 

 sent the last survivals of the gill-opening of a fish-like ancestry. 

 The " arches " which separate the " clefts " are likewise elaborated in 

 human development. The bone (hyoid} which supports the tongue, 

 and the small bones of the internal ear, are the ultimate representatives 

 of the gill arches of our early life. 



Thus we may read, with more than common interest, the story 

 of the genesis of our race, which is written in the progress of our 

 early development, and which should possess for humanity an at- 

 traction far exceeding that contained in any other recital connected 

 with the history of our species. If the facts of our development and 

 of our bodily structure are to be interpreted in a rational sense, the 

 inferences which we may draw from the recital are by no means of 

 doubtful nature. For they tell us at once of descent and ascent of 

 a long ancestry, and of a rise and progress from lower life to the 

 rank and title which humanity legitimately claims as sovereign of 

 the animal kingdom. Such a study not only clearly shows us the 

 perfection to which, as a species, we have attained, but likewise 

 accounts, in the conclusion it formulates respecting our genesis, for 

 the imperfections and rudiments of lower life which, like the re- 



