Co., Virginia Since the name Asellopsis proves to have been 

 preoccupied I propose in its place Maucasellus* retaining M. 

 ienax as the typical species, while the new species may be called 

 M hrachyurus, Irom the short caudal stylets. This species re- 

 sembles M. tenax, described and figured in the Eeport of the 

 United States Commissioner of Fish and Fisheries, Part II, 

 Report for 1872-3, p. 659, plate I, fig. 3, differing principally 

 from It in the following points : The lateral margins of the head 

 are entire; the proximal segment of the caudal stylets is short, 

 being but little longer than the third segment of the antenna ; 

 the rami are also short, the inner being much stronger and 

 somewhat longer than the outer; in the males the propodus of 

 the first pair of legs is armed with a prominent acute tooth on 

 the palmar margin near the base, and, in the appendages of the 

 seventh segment, the terminal portion of the outer pair is 

 smaller and less expanded externally than in M. tenax, and the 

 distal segment of the internal ramus of the inner pair is but 

 little swollen at the base, and approaches the form seen in Asel- 



ity is worthy of mention as being on the Atlantic side of the 

 Appalachian water-shed while M. tenax is vet known only from 

 the Lakes. 



Art. XXXIX.— Pro/«5sor Tyndall on Germs.\ 



The author refers, in an introduction, to an inqury on the de- 

 composition of vapors and the formation of actinic clouds by light, 

 whereby he was led to experiment on the floating matter of the 

 air. He refers to the experiments of Schwan, Schroder and Duseh, 

 Schroder himself, to those of the illustrious Fiench clieinist Pas- 

 teur, to the reasoning of Lister and its experimental verification, 

 regarding the filtering power of the lungs ; from all of which he 

 concluded, six years ago, that the power of developing life by the 

 air, and its power of scattering light, would he found to go hand 

 m hand. He thought the simple expedient of examining hy means 

 of a beam of light," while the eye was kept sensitive by darkness, 

 the character olf the medium in which their experiments were con- 

 ducted, could not fail to be useful to workers in this field. But 

 the method has not been much turned to account, and this year 

 he thought it worth while to devote some time to the more com- 

 plete demonstration of its utility. 



* From maiicuf. maimed, and Asellits. 



t Un the Optical Deportment of the Atmosphere in reference to the l henomena 

 of Putrefaction and Infection. Abstract of a paper read before the Royal Society, 

 January 13th. by Professor TyndaU, F.R.S. From Nature of Jan. 27 and ieb. 3. 



