340 Prof. A. Giard on Parasitic Castration 



In support of this view we may cite here some very correct 

 ideas put forward by Isid. Geoffroy Saint-Hilaire in his 

 * Zoologie gen^rale ' with regard to female birds in male 

 plumage. He says : — 



" We may assume theoretically the existence in most species 

 of birds not of a brilliant plumage proper to the male and of 

 a dull plumage proper to the female, but, in general, of two 

 plumages, one imperfect , belonging especially to the young, 

 the other perfect^ which the males acquire very early and 

 which the females also tend to acquire, but at a much more 

 advanced age and under certain peculiar circumstances " *. 



And further on he adds : — " It has been said that the 

 young of both sexes have the plumage of the female ; but is 

 this statement perfectly correct ? Is it really the case that 

 the male in his youth has the permanent plumage of the 

 female? Or, which is theoretically very different, is it not 

 that the female retains more or less completely the plumage of 

 youth, which, as regards her colours, is arrested in develop- 

 ment and does not arrive at the conditions characteristic of 

 the perfect state of tlie species? " {l. c. p. 492). 



Further, " The old female in the course of those remark- 

 able phenomena which tend to render her more and more like 

 the male, seems to tend to pass through all the same phases 

 which the male pheasant traverses in his youth. A female, 

 when her laying is about to cease or has just ceased, and a 

 young male are in conditions which may be compared in many 

 respects. Both have the same plumage, the imperfect plu- 

 mage; both will have again, at a more or less distant period, 

 the same plumage, the perfect plumage of the species. The 

 same change must therefore take ])lace in both cases, since 

 the starting-point is the same, and the old female and the 

 young male tend towards the same end. But the changes 

 take place with very unequal rapidity in the one and in the 

 other ; one requires several years, a single year suffices for 

 the other. Moreover the order in which the change is effected 

 is not exactly the same. It will be sufficient to compare the 

 young males preserved in all our museums, witli the details 

 that I have given of the old females, to see that in the two 

 cases the change takes place in a different manner. It is 

 never possible to say of an old hen pheasant in which the 

 change has commenced that she has exactly the plumage of 

 a young cock pheasant of such or such an age. It is there- 

 fore by two different ways that nature advances in the one 

 case and the other towards similar final results " (/. c. pp. 507, 

 608). 



* ' Essai de Zoologie gen^rale," 1841, p. 492. 



