PHYSICS AND NATURAL HISTORY OF GENEVA. 2L9 



The same member read a memoir (February 1, 1866) on tlie cJianges of 

 coloration in the feathers of birds. After having studied the structure and 

 development of feathers, the author analyzes the causes which may pro- 

 duce a change of coloration in the same feather, without a moulting having 

 taken place He seeks to explain the variety of colors and reflections by 

 the play of the light falling ou parts differently developed. lie finds in 

 autumn, in every feather, an apparent color and a latent color, and attributes 

 the brilliant coloration of spring to the internal solution of pigmentary granules 

 existing in the interior of the tissues. The humidity of the ambient air tends 

 to swell the cortical substance of the feathers, at the same time that the fat of 

 the body dissolves the latent pigment, which is diffused and colors the feather 

 from the periphery to the centre. The extremities dry up and permit the por- 

 tions which become gradually colored to appear. M. Fatio distinguishes three 

 kinds of feathers — the ordinary, which contain a pigment of the color they affect 

 when seen either by transparence or by incident light ; the optical feathers, which 

 present reflections and contain a brown pigment ; lastly, the enamelled feathers, 

 which, always blue, contain a blackish pigment. Now, in the ordinary and the 

 enamelled feathers it is the barbs which are developed, while in the optical 

 feathers it is the barbulcs which become swollen. The author attributes the 

 luminous effects to a phenomenon of interference ; he compares to colored rings 

 the lines alternately brilliant and obscure, exhibited in incident light by the 

 segments and separating partitions of the optical barbules ; and he explains the 

 blue color of the enamelled barbs by the passage, across a colored transparent 

 layer, of rays i-eflected below by a dark layer tinted in a different manner. He 

 remarks that it would be improper to confound the phenomena of which he has 

 given this account either with those of the discoloration which is observed in 

 some of the palmipeds — a discoloration accompanied by a discharge of the pig- 

 ment, or with the external coloration produced by rubbing in certain birds, or 

 with the discoloration which takes place in collections by the saponification of 

 the fats. Finally, rejecting all idea of a renewal of life in the feather at the 

 time of its second coloration, the author finds in his observations the explanation 

 as well of albinism as more especially of local varieties. (See Mem. de la So- 

 ciete de Phys et d'Hist. Nat , 2d partie, t. xviii, p. 249.) 



M. H. de Saussure presented to the society a work, which he has published 

 in collaboration with M. Sichel, entitled Catalogus Specierum Generis Scoha. 

 He took occasion to observe that among the Scolias the females sometimes 

 vary much from one another, while the males change but little ; so that, in some 

 kinds, it might be said that the females were of different species, while the males 

 are all of one species. This may be explained by the fact that the males exist 

 for little else but the accomplishment of the act of generation, while the females, 

 coming into contact with the various incidents which beset them in the accom- 

 plishment of their proper functions, undergo modifying effects from this circum- 

 stance. M. Humbert made the remark that there are certain gi oups of crusta- 

 ceans in which, on the contrary, it is the males which vary, tlie females remaining 

 the same, a fact which pertains probably to the different part which the males 

 play in the struggle for existence. Dr. ]\Iuller adverted to a circumstance of 

 the same nature in regard to the male and female organs of flowers. M. Ed- 

 ouard Pictet, our new colleague, presented to the society (January 4, 18G6j 

 his Synopsis of the Neuropterce of Spain. 



Personnel. — We have the pain of recording the loss of three of our colleagues 

 — that of M. Perrot, member emeritus ; of ]\l. Frederick Soret, member in ordi- 

 nary ; and of Dr. Montague, honorary member. 



Louis Perrot was born June 30, 1785, of a French family which had settled at 

 Neuchatel at the epoch of the Reformation. His taste for natural history was early 

 developed by reading the Spectacle de la Nature of the Abbe PI ache, a book which, 

 fifty years before, had produced so vivid an impression on the celebrated Bonnet. 



