Vou. II, Pr. IT] LOOMIS—A REVIEW OF THE TUBINARES 33 
IV 
VARIATION 
AGE AND SEASONAL VARIATION 
Natal Down.—Mr. Pycraft has described at some length 
the double natal down occurring in the Tubinares.* He desig- 
nates the outer segment the protoptyle generation and the 
inner segment the mesoptyle generation. As alternative names, 
I suggest primary natal down and secondary natal down. The 
following diagram emphasizes these distinctions : 
Primary natal down or protoptyles 
Natal down or neossoptyles 
Secondary natal down or mesoptyles 
The specimens in double natal down examined by me belong 
to fifteen species, namely, Black-footed Albatross, Galapagos 
Albatross, Laysan Albatross, White-breasted Petrel, .Sunday 
Island Petrel, Black-vented Shearwater, Townsend’s Shear- 
water, Dusky Shearwater, Guadalupe Petrel, Harcourt’s 
Petrel, Leach’s Petrel, Ashy Petrel, Black Petrel, Fork-tailed 
Petrel, Garnot’s Diving Petrel. 
Mr. Pycraft’s statement that it is extremely difficult to dis- 
tinguish the two generations of natal down in the albatrosses* 
is not corroborated in the three albatrosses mentioned above, 
the generations being well defined in each of them. 
If the primary and secondary natal down are not concolor, 
the wearing off of the primary natal down changes the color 
aspect of the nestling. 
Postnatal Plumages.—In certain species of Tubinares the 
juvenal plumage’ is similar in color to the adult one, as in the 
Sunday Island Petrel; in certain other species the color of 
these plumages differs widely, as in the Short-tailed Albatross. 
Much remains to be learned in this group respecting the stages 
of plumage in the progress to maturity. 
Moult.—So far as I am aware, the moult of the Tubinares 
has received but casual attention from ornithologists, Dr. 
Dwight, the leading American authority on the moult of birds, 
and other moult specialists having confined their investigations 
1Godman’s Mon. Petrels, pp. xvii, xviii. 
2 Godman’s Mon. Petrels, p. xviii. ! 
3In part, I have followed Dr. Dwight’s terminology of plumages and moults. 
