THE MUTATION THEORY AND MUTATIONS. 171 



the white triangular mark. The tail-feathers below are also similarly marked, 

 though less strongly. 32 



The eye-streaks are not conspicuous in these birds. The ear-coverts forming 

 a part of the lower streak are buff or pale brown, passing into whitish under the eye. 

 Over the eye no streak is visible, but the portion of this streak lying in front of the 

 eye is present and is whitish. The forehead at the base of the beak is pale-brown or 

 buff. In the back-feathers of 13 some feathers of the second plumage not fully 

 unfolded are intermingled with the first feathers. I found in some of these new 

 feathers some persistent traces of the turtle-dove pattern, in the form of two lateral 

 dark spots on the basal half of the feather. I then examined the Juvenal feathers in 

 the same place (near the rump), and also found faint outlines of the spot-areas there." 

 This seems of some interest, as spots have disappeared in this as in other species." 



ON THE JUVENAL PLUMAGE COLORS or A "MUTANT" AND NORMAL ZENAIDA. 



A juvenile Zenaida vinaceo-rufa (21) presents an interesting "mutation." This 

 bird was hatched September 28, 1906. The front and sides of the head, neck, breast, 

 and abdomen; the wings, scapulars, and under tail-coverts; and even the tail- 

 feathers (below), are all marked with this mid-terminal, triangular white spot, 

 which is the characteristic mark in the wing of the guinea-pigeon (pi. 84, fig. B). 



This bird is just a little larger than 20 (which is of normal color, hatched August 

 18, 1906, from the same parents), but only a little younger. Both birds are now 

 (November 9, 1906) in Juvenal plumage and can be compared and photographed 

 side by side. No one would take them for the same species, and yet they are from 

 the same pure-bred parents. 



I expect that these marks will disappear in the adult plumage. 85 If they do, 

 then we have what might be called a "juvenal-stage mutation"; in other words, 

 a character with all the appearance of a mutation, but transient. (See adult normal 

 Zenaida vinaceo-rufa, pi. 83, fig. A, and adult Z. amabilis, pi. 87.) 



It is important to know if this character is entirely new, or is it a great enlarge- 

 ment of a minute feature of the normal Juvenal feathers. On this point the photo- 

 graph of 20 supplies evidence (see pi. 84, fig. A); it shows just a beginning of this 

 character on the neck just a mere line. 36 This terminal dividing-mark is not white 

 in the normal form, but pale buff or pale brown. 37 I have seen the same mark nearly, 



32 Several of these feathers were plucked and preserved. From their appearance, and the above description, one 

 would strongly suspect, after the test with mutant 21, that the lesser degree of the guinea-mark exhibited by this 

 bird (14) would also have perpetuated itself in its offspring. It is almost certain that the bird was not bred, and it 

 probably died young. On the basis of the above description, I have ventured to question (table 6) the "normality" 

 of this individual. ED. 



33 These feathers were removed and mounted, but were never figured. After 11 years the outlines of these spots 

 can still be seen. ED. 



34 The feathers in the median back region of the European turtle-dove have "dark centers," especially on the rump. 

 36 This prediction proved entirely true. ED. 



36 Further evidence of the beginnings of the mark in Zenaida young has already been given in the preceding 

 pages. ED. 



37 From a Zenaida x Zenaidura hybrid (ZZC), which was hatched one day later than the mutant Zenaida (21) , 

 feathers were taken (from the same regions which were strongly modified in the mutant) for comparison with the 

 latter. The following conditions were found: "The median buff or fawn streaks sometimes found in these feathers 

 are not at all conspicuous, but they are evidently homologues of the mark seen in the Zrnai'ln mutant. In a feather 

 taken high up on the (right) side of the neck the mid-area is indistinct, but about 2 mm. wide at the tip; here, however, 

 "gray" is so intermixed (with buff) that there is really no clear figure. A feather from just below the preceding shows 

 the same mixed condition. Four other feathers from still lower on the neck show no apical figure, though there is a 

 glimmer of buff in the form of a figure widening apically. In an upper tail-covert there is no sign of a figure." Of 

 another similar hybrid (ZZ 2, sister to the above, see table 91, Vol. II) the author had earlier written (May 1905): 

 "On the breast-feathers there is a reddish mid-streak (as in Leptoptila), which is wider at the tip, gradually narrowing 

 inward to a point. The reddish is seen at the middle of the tips of the primaries, though there it is not regular in 

 form, as on the breast. It is found also in the primary coverts. The nest-mate of this bird is quite similarly marked. 

 It looks as if this was the way the black center became divided into two lateral spots. If so, it is essentially as in the common 

 pigeon and in Columba livia." 



