r Auk 



144 Huxley, Bird-watching and Biological Science. LApril 



deeply in me the conviction that birds have a mind of the same 

 general nature as ours, though of course more rudimentary : if they 

 are automata, then so are we. Prof. Washburn's book reaches the 

 same conclusion. As far as the problems of sex are concerned, 

 bird-watching has lead me to important ideas, and has gradually 

 made me believe that in birds at any rate an individual of either 

 sex contains within itself the characters of the other sex in a latent 

 condition.^ With which preface let us plunge in medias res. 

 It is an old idea, and a favorite of Sir Thomas Browne, that 



' This is not the place to discuss the theoretical aspects of the problem of sex. However, 

 it will he well to mention one or two ideas to which such studies as these have led me. 



Morgan, in his recent book just cited, brings forward various facts, largely as the results 

 of castration experiments, to show that the mechanism of sex delerminalion is entirely differ- 

 ent in birds and in mammals (and again in insects). This is an important and notabls fact, 

 but in considering its bearings we must not be led to forget another equally important fact 

 that emerges especially as the result of a comparative observational study — namely, that 

 all the determinants for the sexual characters of both sexss are present complete in each 

 individual of either sex (with certain exceptions when the male has different sex-chromo- 

 somas from the female), that this holds good for both birds and mammals, and that the 

 different results in the two groups are due to differences in the method by which in any 

 individual the right characters are brought out, the unneeded ones inhibited. This is 

 shown very well by the fact that the requisite mechanism for the copulatory actions of 

 both sexes appears to be present in individuals of both sexes. For instance, I learn from 

 my friend Mr. W. M. Winton that he has personally seen two cases of bitches where ovari- 

 otomy was followed by the acquisition of male actions. Similar actions in non-operated 

 female animals are familiar in cows (MuUer, Sexiialbiologie), and are recorded for rabbits 

 (Washburn, in lilt:). Pearl and Surface have recently recorded (Science, April 23, 1915) a 

 most interesting case where a cow assumed not only the behavior bui also the appearance 

 of a bull, owing to cystic disease of the ovaries. These examples alone will show that in 

 mammals the female carries within herself the determinants for the characters of the oppo- 

 site sex, just as Morgan's results show the converse of this to be true. 



In birds, the facts assembled by Morgan show at once that the f 2male carries the determi- 

 nants for male characters. For the converse proof, I have myself assembled some records 

 where the male performs female actions (and vice versa), in my paper on the Grebe (Huxley, 

 '14). The case of the Phalarope is, from a different point of attack, proof positive that the 

 determinants for female character., are present in the male. In all species of Phalaropes 

 (PhalaropodidcP), while both sexes assume special plumage during the breeding season, and 

 while this breeding-plumage is of the same general pattern in both sexes, and is obviojsly a 

 recent acquisition in evolution, yet the female is larger and much brighter than the male, 

 and in addition does all the courting The only interpretation of these facts appears to me 

 to be that, just as in most sexually dimorphic birds the male has acquired certain colors 

 and structures, and that these have come to be shared by the female in lesser degree (Cardi- 

 nal and many other Finches, Bob-white and most other Odontophorida;, many Woodpeck- 

 ers, Yellow-headed Blackbird, Dickcissel, Scissor-tailed Flycatcher, etc.), so here sexual 

 selection has helped the female towards her bright plumage, and the male has automatically 

 come in for his share. The results are best interpreted if we suppose (as is cytologically 

 reasonable) that the determinants for the characters, even though the characters themselves 

 are acquired primarily by one sex only, at once come to be present in the germ-plasm of 

 both sexes. Suppose it to be the male which acquires the secondary sexual characters. 

 After this there are two possibilities. Either the inhibition in the female will not be suffi- 

 cient to restrain some appearance of the new characters in her, even from thj start: or else 

 in some unexplained way the inhibition will gradually weaken and the female come in the 



