180 Degeneration in the Ostrich 



Africa, a mutual struggle for existence is inconceivable ; " either a feast 

 or a famine," applies to the ostrich as to many other things in Africa. 



If the losses have little or no bearing on the welfare of the ostrich 

 natural selection has necessarily been inoperative in directing their 

 course ; they are wholly intrinsic and independent of any external 

 modifying cause. Moreover, as the same mutative changes are going 

 on concurrently throughout the race, no important individual differences 

 will arise such as would afford material on which natural selection could 

 be exercised ; natural selection may wipe out the race, but can not guide 

 its evolution. The slight differences in the rate of retrogression which 

 afford us the details of the manner in which it is proceeding are altogether 

 too insignificant to count in the broad, competitive life of the ostrich. 

 Natural selection is powerless to check permanently the relentless, 

 degenerative influences which are at work, and when the retrogressive 

 changes have gone sufficiently far to interfere with the activities essential 

 to its existence the ostrich will disappear as a race. 



Ontogenetic and Phylogenetic Degeneration. 



Factorial changes are held to be effected during the complicated 

 mitotic processes of gametogenesis and fertilization which intervene 

 between one generation and the next, and the hereditary differences in 

 the new generation are determined at that time, and are uninfluenced 

 during ontogeny. The conceptions underlying the phrase " non-inherit- 

 ance of acquired characters " apply equally well to structures in a 

 changing state as to those which are fixed and stable. The process of 

 degeneration is in no ways effected during the life-time of the individual, 

 but only with the formation of the zygote. On embryos and newly 

 hatched chicks the plumes, scales, and claws are to be found in exactly 

 the same degenerative phases as in the adult. 



From the many directions along which degeneration has taken place 

 several considerations emerge when the changes are viewed in their 

 relationships to ontogeny and phylogeny, such as the question of the 

 ontogenetic period of factorial expression, and also factorial persistency 

 and atrophy. Whatever be their nature the Mendelian factors are held 

 to reside in the germ cell, and to be part and parcel of it ; we can also 

 suppose that they exercise their influence upon the developing organism 

 as part and parcel of the somatic cells ^ and ordinarily maintain it 



1 Prof. T. H. Morgan when discussing Weismann's Praeformation Hypothesis and the 

 Factorial Theory in his Mechanism of Mendelian Heredity (p. 225) remarks as follows : 



