474 



THE EVOLUTION OF LIFE. 



bearing fibres, each of which, again, bears a fringe of down. 

 But in some birds, as in the ostrich, various stages of 

 arrested development of the feathers may be traced : between 

 the unusually-elaborated feathers of the tail, and those about 

 the beak which are reduced to simple hairs, there are transi- 

 tions. Nor is this the extreme case. In the Apteryx we see 

 the whole of the feathers reduced to a hair-like form. Again, 

 the hair which commonly covers the body in mammals is, 

 over the greater part of the human body almost rudimentary, 

 and is in some parts reduced to mere down — down which 

 nevertheless proves itself to be homologous with the hair of 

 mammals in general, by occasionally developing into the 

 original form. Numerous cases of aborted organs are given 

 by Mr. Darwin, of which a few may be here added. " No- 

 thing can be plainer," he remarks, "than that wings are 

 formed for flight, yet in how many insects do we see wings so 

 reduced in size as to be utterly incapable of flight, and not 

 rarely lying under wing-cases, firmly soldered together ? " . . . 

 " In plants with separated sexes, the male flowers often have 

 a rudiment of a pistil ; and Kolreuter found that by crossing 

 such male plants with an hermaphrodite species, the rudi- 

 ment of the pistil in the hybrid offspring was much increased 

 in size; and this shows that the rudiment and the perfect pistil 

 are essentially alike in nature." And then, to complete. the 

 proof that these undeveloped parts are marks of descent from 

 races in which they were developed, there are not a few direct 

 experiences of this relation. " We have plenty of cases of 

 rudimentary organs in our domestic productions — as the 

 stump of a tail in tailless breeds — the vestige of an ear in 

 earless breeds — the re-appearance of minute dangling horns 

 in hornless breeds of cattle." (Origin of Species, 1859, pp. 

 451,454.) 



Here, as before, the teleological doctrine fails utterly; for 

 these rudimentary organs are useless, and occasionally even 

 detrimental ; as is the appendix vermiformis, in Man — a part 

 of the caecum which is of no value for the purpose of absorp- 



