68 ORTHOGENETIC EVOLUTION IN PIGEONS. 



spots are absent in the first plumage, or so nearly so as not to be visible to surface 

 examination. 8 In the related red ring (St. hnmilis) all of the young have these 

 spots in the first plumage. 9 This species has more pigment, hence enough to appear 

 in the first feathers. The Japanese ring (St. douraca) is darker than the common 

 blond ring, and therefore more often — almost invariably — has spots in the first 

 feathers. The Damar ring-dove (St. damarensis) is another form more pigmented 

 than the blond ring; in this dove (pi. 19, fig. B) the mark is quite strong in the 

 juvenal feathers and is plainly lateral. 



In these neck-marks of the collared ring-doves we have, therefore, a good ex- 

 ample of a character which appears earlier in the ontogeny than in the phylogeny — 

 a tendency to appear earlier — what first came in second feathers now comes in the 

 first feathers. 10 



The neck-marks of the five groups into which Salvadori 11 divided the former 

 genus Turtur were somewhat inaccurately or inadequately described. These groups 

 were designated: (1) Turtur, (2) Homopelia, (3) Streptopelia, (4) Spilopelia, (5) 

 Stigmatopelia. Groups (4) and (5) are stated (p. 396) to have bifurcated neck- 

 feathers. 



Spilopelia: ''Feathers of the hind neck bifurcated, black, with two ichite apical spots." 

 Stigmatopelia: ''Feathers of the fore neck bifurcated, black, with two rufous apical spots." 



It is strange that Salvadori should entirely overlook this feature in Homopelia. 

 Mr. T. H. Newman 12 calls attention to this oversight, and also refers to Temminck 13 

 as having given a separate figure of one of the bifurcated feathers. 



These homopelias are very interesting cases, as they have bifurcated neck- 

 feathers, sometimes on the sides and back of the neck, and sometimes on both sides 

 and front of the neck. The latter seems to me to be a departure from the rule that 

 such marks are limited to the side and back of the neck. 



8 The black ring or collar in the blond ring (St. risoria) is sometimes narrower at its middle, on the back of the 

 neck, than at the ends. This fact, together with the complete interruption of the ring on the back of the neck in the 

 first plumage, by which it is broken into two portions— one on each side of the neck, beginning a little below and 

 behind the ear-coverts, and growing narrower backward— suggests that the half-ring has arisen by the extension of two 

 spots like those seen in the turtle-dove. This ring is creamy white in the white ring (St. alba). It is often reduced 

 to a mere shadow, or wholly absent, in the first plumage (see Chapter XVII, and plate 31, Vol. II). 



9 For the juvenal neck-marks of the risoria X humilis hybrids, see text-fig. 9 of Vol. II.— Ed. 



10 Darwin (Descent of Man, Vol. II, p. 153) points out the fact, and makes frequent use of it, that "variations 

 occurring at different ages are inherited at the same age." And, further: "Variations which occur late in life are 

 commonly transmitted to the same sex in which they first appeared; while variations occurring early in life are apt 

 to be transmitted to both sexes; not that all the cases of sexually-limited transmission can thus be accounted for." 



From the standpoint of the present, all inheritable variations are in the germ. The order in which they come 

 to sight is the order in which the germ has been modified — not the order in which a new unit-character was added, but 

 the order in which the germ as a whole was modified. 



Darwin's reasoning on the "lopping of the comb" in the hen of Spanish fowl (pp. 151-152) is characteristic of 

 his viewpoint. My idea is that the difference here between the sexes is merely one of strength. 



Darwin says, too (p. 148), that "characters which are limited in their development to one sex are always Intuit 

 in the other." He had elsewhere written (Origin of Species, p. 12): "A much more important rule, which I think 

 may be trusted, is that at whatever period of life a peculiarity first appears, it tends to reappear in the offspring :it 

 a corresponding age, though sometimes earlier. In many cases this could not be otherwise; thus the inherited pecu- 

 liarities in the horns of cattle appear only in the offspring when nearly mature ; peculiarities in the silkworm are known 

 to appear at the corresponding caterpillar or cocoon stage. But the hereditary diseases and some other fads make me 

 believe that the rule has a wider extension, and that, when there is no apparent reason why a peculiarity should appear 

 at any particular age, yet that it does tend to appear in the offspring at the same period at which it first appeared in 

 the parent. I believe this rule to be of the highest importance in explaining the laws of embryology." 



" ( 'atalogue of birds in the British Museum, Vol. XXI, 1893. 



I? Avicult. Mag., Jan. 1908, p. 80. 



" Hist. Nat. Gen. des Pig. PI. Col. 242, 1823. 



