94 EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 



Beauperthuy and Adet de Roseville addressed some observations at 

 the sitting of the Academy of Science, Paris (19th March 1838), 

 tending to prove that putrid decomposition is preceded by the develop- 

 ment of microscopic animalcules ; these are first of the genus Monas, 

 and ultimately become Vibriones, which multiply with considerable 

 rapidity. 



[From the Annales des Sciences Naturelles, Jan. 1840.] 



M. P. Gervais on several Species of the Order Acaridte. In this 

 paper two new species, (with figures), are added to the genus Scirus, viz. 

 S. obisium, which is very small, not exceeding one- third of a millimetre 

 in length, devoid of eyes, bright orange colour, and nearly transparent, 

 &c. The other, S. hexopthalamus, having six eyes of a carmine colour ; 

 larger than the preceding ; of an uniform orange colour. They were 

 both found near Paris. 



A species of the genus Dermanyssus, named from being met with on 

 Pipistrella, D. Pipistrella, is also figured. Its length is about one milli- 

 metre, and is much smaller than the genus Caris. He has also figured, 

 for comparison, Psoroptes equi, Sarcoptes hominis, and S. dromedarii ; 

 the latter was obtained from the scaly crust of a dromedary recently 

 sent from Africa to the Jardin-du-Roi. No resemblance is to be per- 

 ceived between that of the camel and the horse ; whilst the first, on 

 the contrary, so closely resembles that of man, that it may be mistaken 

 for it if not examined with care ; and it may be supposed, that it is to 

 this similarity of structure that it passes from the animal to which it is 

 peculiar, and lodges itself, with the greatest ease, conveying the disease 

 from the one to the other. On careful examination, however, under high 

 powers, M. Gervais considers that sufficient characters may be found 

 to entitle it to the place of a species. In this paper the differential cha- 

 racters are given in detail ; it is accompanied with a beautiful plate, 

 on which seven species of the order are delineated. 



Duvernoy on some points in the structure of Limulus, with a more par- 

 ticular description of their branchite. This memoir, which is of some 

 length, enters into the historical, descriptive, and theoretical parts of 

 the subject. 



Lallemand's paper on the origin and mode of development of Zoos- 

 perms, is inserted entire, for an abstract of which see p. 59 of this 

 Journal. In some remarks which precede the paper, he states, that a 

 single drop of fluid is sufficient for a perfect observation, a larger quan- 

 tity being inconvenient. It is requisite to press the small piece of thin 

 glass which covers it, to stop the currents of air there established, and 

 to cause the bubbles of air to disappear which are there found imprisoned. 

 Although the two glasses appear to touch, the Zoosperms move in the 

 intervals with great freedom, as long as they have the power, and the 

 evaporation has not proceeded to a too great extent ; should this take 

 place, a drop of water added, for some time prolongs their move- 

 ments. 



