24 THE WHENCE AND THE WHITHER OF MAN 



but even in tlie proportion of their limbs, their toes, 

 etc. It may therefore be considered as a general fact 

 that the phases of development of all living animals 

 correspond to the order of succession of their extinct 

 representatives in past geological times. The above 

 statements are quoted almost word for word from Pro- 

 fessor Agassiz's "Essay on Classification." The larvae 

 of barnacles and other more degraded parasitic Crusta- 

 cea are almost exactly like those of Crustacea in general. 

 The embryos of birds have a long tail containing almost 

 or quite as many vertebrae as that of archaeopteryx. 

 But most of these never reach their full development 

 but are absorbed iato the pelvis, or into the " plough- 

 share " bone supporting the tail feathers. Thus older 

 forms may be said to have retained throughout life a 

 condition only embryonic in their higher relatives. 

 And the natural classification gave the order not only 

 of geological succession but also of stages of embry- 

 onic development. Thus the system of classification 

 improved continually, although more and more inter- 

 mediate forms, like archaeopteryx, were discovered, 

 and certain aberrant groups could find no permanent 

 resting-place. 



But why should the generalized comprehensive 

 forms stand at the bottom rather than the top of the 

 systematic arrangement of their classes ? Why should 

 the system of classification coincide with the order of 

 geologic occurrence, and this with the series of embry- 

 onic stages? Above all, why should the embryos of 

 bird and perch form their tails by such a roundabout 

 method? Why should the embryo of the bird have 

 the tail of a lizard ? No one could give any satis- 

 factory explanation, although the facts were undoubted. 



