gape, a thick skin, puckered and folded, forms a large rosette of an orange-yellow. The appendages of the eyelids consist of a wide, thick border of vermilion, and two horny flakes of iron-grey, one above triangular, the other beneath elongated (horizontally).
"Let us now see the aspect presented by the adult Puffin in winter, or after the breeding season.
"The beak is smaller, as if sliced off (lronqu4) in front, and especially at the lower mandible, which then forms a broken Hue instead of a regular curve (fig. 2). The two very distinct parts which 1 have pointed out as existing in the adult in spring, may be here recognized, the one posterior, strangely modified by the fall of the nine horny pieces above-mentioned; the other anterior, which has remained unaffected.
"1. The posterior part has lost somewhat of its thickness and consistency ; it is re-covered with a thick skin which presents, on the upper mandible (fig. 2), a membranous pleat (a') and the nasal membrane (b'); on the lower mandible, the membranous band (f') and the sheathless chin (g').
"2. The anterior part has undergone no modification ; it remains as it was in the breeding season.
"The rosette at the gape is reduced to a narrow baud of pale yellow. The free edge of the eyelid has lost colour, and the horny flakes are wanting."
Dr. Bureau here furnishes a tableau in which these two con- ditions of Fratercula arctica in spring and winter, as well as the slight modifications which the plumage undergoes at those seasons, are set forth in parallel columns. He then proceeds, under the head of "Transformation du Bec," to point out the mode in which the various pieces of the beak are respectively shed or cast.
The adult bird, he observes, owes its summer dress to phenomena of three kinds — hypertrophy, formation of horn, and coloration ; and loses it under the influence of three inverse phenomena, namely, atrophy, loss of horny substance, and loss of colour.
He concludes by showing that analogous phenomena occur in the allied species Fratercula glacialis, F. corniculata and remove Lunda cirrata.
