characteristic types, one of which was met with in spring and the other in winter.
"The disappearance of the former type of Puffin just as the latter arrived, the presence in each of specimens evidently adult, the exact correspondence in size, speedily suggested that neither of the views above stated could be quite correct. The discovery of two large colonies of these birds on the coast of Brittany shortly strengthened my conclusion.
"I had, in a word, arrived at the conviction that the views in question were erroneous, without seeing my way to a satisfactory solution, when a careful examination of the beak, gape and pal- pebral appendages led me to suspect that these parts must be subject to a complete metamorphosis after the breeding season. The more I examined the pleat (ourlet), the rosette at the base of the bill, the horny plates to the eyelids, the more evident did the metamorphosis appear. Hut how did this phenomenon come about? Was it effected only when the birds had reached the high seas, or was it for me to witness it in the birds which were the last to quit their breeding places? Of this I remained ignorant until quite lately.
"In June, 1876, during a visit which 1 made with my brother to these colonies of Puffins, the examination of a large number of living birds strengthened my convictions, and I resolved to return shortly in time to witness the metamorphosis. My choice lay between the lie de la Manche and the Ile de l'Ocean, and although the former was frequented by a much larger colony, I selected the latter in the hope of obtaining on the same rock the young of the Roseate Tern (Sterna Duogalli).
"Although at that time 1 was occupied in Paris with my physiological studies, 1 started without hesitation on the 25th August, 1876, and on the 27th I crossed to the outskirt of the island, which rises above the sea in a majestic arch. But rough weather often prevails on this wild sea-board, abounding in shoals. The sea, running high with the tide and north-east wind, broke over the only accessible point, and it was therefore impossible to think of landing ; besides it would have been labour lost, for the rock was deserted. In the hope of finding some loiterers I explored in vain the shores of the island ; all, old and young, had already taken their departure, and the Roseate Terns were also gone. My journey therefore was fruitless: I had come a fortnight too late.
