No. 627] GERM, PLASM OF THE OSTRICH 327 



but on only a few soutliern birds is it ever seen, and tlien 

 in a most vestigial state, barely showing beyond the skin. 



What may doubtless be regarded as the first steps in 

 the degeneration of the big middle toe are also displayed. 

 Down the front of the tarsus extends a series of large, 

 nearly rectangular scales, continuous all the way from a 

 little below the ankle and passing over the upper surface 

 of the toe, though usually somewhat smaller where the toe 

 joins on to the tarsus. In a few ostriches a distinct break 

 occurs at the joint, several large scales being altogether 

 wanting (Fig. 3), and rarely birds are met with in which 

 a second break takes place over the middle joint of the 

 toe. One may hazard the suggestion that the interrup- 

 tion in the scutellation over the two joints has an adaptive 

 significance, allowing the parts to move more freely, but 

 we have also to face the fact that the single break occurs 

 in but a few while the double break is very rare. It is 

 presumably a new feature in course of introduction into 

 the ostrich race, but not yet established for the members 

 as a whole. It involves however a reduction in the make-up 

 of the toe ; it is a minus or retrogressive mutation, and 

 may well be the first hint of impending loss of what will 

 be the only toe when the small fourth has gone. 



Although definite experimental data on all these reduc- 

 tion phenomena are not yet available everything points 

 to the fact that the variations breed true and are therefore 

 germinal in their nature: they are certainly not ordinary 

 fluctuating somatic variations. Proof is to hand that the 

 42-plumed cock has factorial representation for its high 

 number of plumes. Another similarly numbered hen is not 

 yet available, but in crosses with various 36-plumed hens 

 the average number of plumes of the progeny is 39.56 

 which is midway between the parents, while the mode is 

 40. Considering the heterozygous nature of the ostrich 

 where number of plumes is concerned a fluctuating series 

 of this kind is what would be expected. Only one farmer 's 

 strain has the nearly complete second and third rows of 

 under-coverts, but they are found in all the progeny from 



