No. 627] GERM PLASM OF THE OSTRICH 



a cause of genetic variations . . . a purely external agent, 

 the continued selection of personal somatic qualities, will 

 alter the germ plasm." 



It seems to be generally allowed that at any period the 

 majority of forms of life are static so far as gonninal 

 alterations are concerned, while some are undergoing 

 progressive changes and others retrogressive changes. 

 During the present period the representatives of the 

 widely distributed Batitae are unquestionably undergoing 

 marked changes and have been for ages past. The 

 changes are in a negative or retrogressive direction, and 

 express themselves in somatic degeneration, particularly 

 with regard to the wing and shoulder girdle. The living 

 Apteryx is a well-known instance of wing degeneration, as 

 also the recently extinct moas, in which no hint of a wing 

 has been found and a trace of the glenoid cavity only in 

 one species. From the data already submitted we are 

 able to learn something as to the manner in which the 

 degenerative processes are proceeding in the wing and leg 

 of the ostrich, and presumably the same method holds for 

 the Ratit« generally. Factors are evidently in process of 

 dropping out, in regular succession, along definite pre- 

 scribed lines, the degree varying much when the entire 

 race is taken into account. 



All Mendelian writers seem to concede that the fac- 

 torial changes, plus or minus, are not autonomous on the 

 part of the factors, but are '*a result either of wholly 

 internal physiological causes, or of very extraordinary 

 environmental stresses acting directly upon the germ 

 cells." Though the results of Morgan and his associates 

 indicate that it may yet be possible to understand the 

 manner in which the factors undergo th(Mr cliMmres it will 

 always be competent for us to cn(|iiiro ;is to the cause or 

 causes inducing the changes. To be coiiiiilcic om- ;ii!al\>is 

 of variability will need to get bcyoiKl tlio factor- to the 

 force or forces acting upon thcui. In tiic pi-c\lou- sec- 

 tions good reason lia> been adduced t"oi- >ui.j»(K-iim- that 

 the losses going on in the germ pla^ni ot" the ostricli are 



