1879.] MR. P. L. SCLATER ON CERTAIN PARROTS. 299 



unknown cause at an unusually early age in the males, and their 

 consequent transference to both sexes." ' 



That sexual selection has played a very important part in the 

 subsequent development of the horns and antlers of the Pecora there 

 can be no reasonable doubt ; but the known facts appear to me to 

 indicate that they were probably first developed in both sexes as 

 organs of defence against common enemies. They are present in 

 the females of the Camelopardalidce, in those of all the Bovidce except 

 twelve genera of Antilopince-, and in those of one genus of the 

 least-specialized section of the Cervidce, while we have seen that 

 they are not unfrequently abnormally developed in the two other 

 genera of the same section with which we are best acquainted. The 

 same abnormality, it may be added, occurs in at least one of the 

 genera of Antelopes, in which the females are usually hornless 3 . 



On the assumption that the antlers and horns of the Pecora were 

 first developed in the males only, their presence in the females of 

 so many forms can only be explained by the hypothesis that " an 

 unknown cause " has led to their transference from the other sex. 

 On the other hand, if they were at first common to both male and 

 female, the problem appears to me to be capable of a more satis- 

 factory solution. In the males they would naturally be further 

 developed by sexual selection, and in the females the strain on the 

 constitution would tend to their reduction or even elimination — this 

 strain, as Mr. Darwin himself has pointed out, being much the 

 greatest in the Cervidce, in which the weapons require to be renewed 

 every year. That they should be retained (usually in reduced size) 

 by the females of most of the forms with non-deciduous horns appears 

 therefore to be natural ; while their retention in the female of the 

 Reindeer, and their occasional abnormal development in those of other 

 little-specialized Deer, is no more than we should expect on the 

 doctrine of heredity. 



3. Remarks on some Parrots living in the Society's Gardens. 



By P. L. Sclater, M.A., Ph.D., F.R.S., Secretary to the 



Society. 



[Eeceived March 13, 1879.] 



(Plate XXVIII.) 



During the preparation of a new edition of the List of Vertebrates 

 in the Society's Collection I have, as on former occasions of a like 

 nature 4 , made several notes referring to special rarities and neces- 

 sary charges in nomenclature of the Psittacidse, which I beg leave 

 to offer to the Society. 



Our series of Psittacidse at the present moment consists of about 

 J.70 individuals, belonging to 98 species, amongst which, besides those 



i Tom. cit. p. 504. 2 Sir V. Brooke, P. Z. S. 1878, p. 884. 



3 Blyth, as quoted by Mr. Darwin, ' Descent of Man,' p. 505. 

 *■ Cf. P. Z. S. 1867, p. 183, et 1871, p. 493. 



