162 [Sept. 



September 9th. 



Dr. Bridges, Vice President, in the Chair. 



A paper was presented entitled, " Researches upon the Cyprinoid 

 Fishes inhabiting the fresh waters of the United States of America, 

 west of the Mississippi Valley, from specimens in the museum of the 

 Smithsonian Institution, by Charles Girard, M. D.," which was re- 

 ferred to a Committee consisting of Drs. J. A. Meigs, Rand, and 

 Hallowell. 



September IQth. 

 Mr. Lea, Vice President, in the Chair. 



Letters were read 



From the Royal Academy of Sciences of Madrid, dated December 

 31st, 1854, transmitting their publications acknowledged this even- 

 ing. 



From the Smithsonian Institution, dated Washington, June 18th, 

 1856, acknowledging the receipt of Vol. 8, No. 2, of the Proceedings 

 of the Academy. 



From the American Philosophical Society, dated September 3d, 

 1856, acknowledging the receipt of the Journal, (N. S. Vol. 3, part 2,) 

 and the Proceedings (Vol. 8, Nos. 1, 2, 3), of the Academy. 



Dr. Leidy remarked that, he had observed the eyes of the Katy-did {Flaty- 

 phyllum concavum) which during the day are translucent and greenish, at night 

 assume a deep cherry red color. Upon experimenting with the insect he found 

 that, when the light was excluded, in the course of a few hours the eyes gradu- 

 ally became dark red, and after a restoration of light they again became trans- 

 lucent and greenish. The phenomenon was not positively explained, but it was 

 supposed to belong to the same category of changes, observed in the skin of 

 certain reptiles and cephalopoda ; /. e. the coloring matter of the eyes probably 

 is composed of chromatophora, or contractile pigment cells, which according 

 to the condition of contraction exhibit a difference in color. 



Dr. Leidy also directed the attention of the members to several shells of the 

 oyster and clam [Ostrea virginiana and Venus mercenaria) much perforated, 

 which are common on the ocean shore, where they are noticed by all visitors. 

 Dr. L. had for a long time suspected that the perforatiocs were due to some 

 other molluscous animal or a worm ; and he had frequently sought for them. 

 The last summer, in dredging, in company with Mr. Ashmead and Prof. Baird, 

 on an old oyster bed, at Great Egg Harbor, New Jersey, a large number of these 

 perforated shells were obtained, and all of them were observed to be occupied 

 by a sulphur yellow sponge of the genus Cliona. This boring sponge forms an 

 extensive system of galleries between the outer and inner layer of the shells, 

 and protrudes through the perforations of the latter tubular processes, from one 

 to two lines long and one-half to three-fourths of a line wide. The tubes are 

 of two kinds; the most numerous being cylindrical aud expanded at the orifice 

 in a corolla form, with their margin thin, translucent, entire, veined with more 

 opaque lines, and with the throat bristling with silicious spicule. The second 

 kind of tubes are comparatively few, about as one is to thirty of the other, and 

 are shorter, wider, not expanded at the orifice, and the throat unobstructed 



