290 



1857 ; Smithsonian Institution, June, 1857, acknowledging the 

 receipt of the Proceedings of the Society ; Verein fiir Natur- 

 kunde in Nassau, March 1, 1857 ; Cambridge Philosophical 

 Society, February 26, 1857 ; K. Akademie der Wissenschaften, 

 Wien, November 24, 1856, presenting their various publications. 

 From Prof Joseph Lovering, July 20, presenting, in behalf of 

 the American Association for the Advancement of Science, its 

 Proceedings ; Academy of Natural Sciences, June 19, asking for a 

 missing number of the Journal ; the Georgic Association, Ran- 

 dolph, N. Y., July 21, asking for the publications of the Society ; 

 Geological Museum, Calcutta, January, 1857, making the same 

 request, and sending its own Memoirs ; and from James H. 

 Slawson, Houghton, Michigan, acknowledging his election as 

 Corresponding Member. 



DEPARTMENT OF MICROSCOPY. 



Mr. John Green exhibited a large number of thin sec- 

 tions of the Bush Ropes, so called, — peculiar woods ob- 

 tained by him in Surinam, and made some extended 

 remarks upon their method of growth. He said he was 

 preparing a paper upon the subject, which he should read 

 when his examinations are completed. 



Dr. James C. White exhibited the Eggs of the Itch 

 Insect, Sarcoptes ho7}iinis. 



He remarked that, as is now well known, it is the female only 

 which burrows. She bores transversely downwards through the 

 skin, but never to a great depth beneath the surface. Each day 

 as she moves onward she leaves an egg behind her. After she 

 has deposited fourteen, the larva of the first matures and creeps 

 out upon the surface, there to ramble with the other young and 

 males till maturity, when if a female, and after copulation with a 

 male, also an outsider, it repeats the process above mentioned. 

 Each day a young one emerges from the burrow, leaving behind 

 the membranous walls of its cell. The acarus may thus extend 

 its hole indefinitely, even to the extent of four inches, and its 

 course may be traced by a white elevated line on the skin. It 



