Nova Acta AcademicB Natura; Curiosorum. 257 



** Ei der Schnecken," we have the continuation of a series of observa- 

 tions by that skilful and minute anatomist on the rotatory motion of the 

 embryo in the ova of land and fresh water spiral shells. The principal 

 results deduced from the microscopic examination of the eggs of Limncea 

 stagnalis. Helix Pomatia, and Paludina vivipara, in various stages of 

 growth, consist in the following facts. First, that the embryo floating in 

 the albumen possesses, up to a certain period of its developement, a 

 distinct rotatory motion. Secondly, that this motion is produced by the 

 impulse of the fluid, which is constantly propelled into a sort of sinus 

 on the right side of the animal, corresponding to the branchial aperture. 

 Thirdly, that the n)Otion of the fluid is derived, in a great measure, if 

 not entirely, from the impulse which it receives from the embryo itself. 

 In the ova of Paludina the motion was observed to continue for some 

 minutes after the transparent shell had been ruptured, and the fluid con- 

 taining the embryo suffered to escape, and to mix with the water upon 

 the stage of the microscope. In this situation, however, it became gra- 

 dually weaker and less regular, and was soon altogether lost, although 

 the embryo still continued to live. Within the unbroken shell, Dr. 

 Carus has seen the rotatory motion continue without intermission and 

 with perfect regularity for an hour together. 



M. Risso's " Observations sur quelques nouvelles esp^ces de Crustaces 

 " de la mer de Nice," require but a brief notice at our hands. The 

 new species consist of one PeneuSf four Mphei^ and one PalcBmon, of 

 which the first, and two of the second, are figured. 



As little need be said of the " Gryllorum Hungariae indigenonmi spe- 

 " cies aliquot (quas) illustravit Franciscus Liber Baro de Ocksay." The 

 " species aliquot" are two in number ; the one, G. crassipesoi our au- 

 thour, already published in M. Charpentier's Horcs EntomologiccB ; and 

 the other, G. h-achypterus, altogether new. The illustration extends no 

 farther than a brief description. 



The next article which comes under our notice is one of considerable 

 extent, occupying no less than 238 pages of the volume ; and is distin- 

 guished by patient research, minute investigation, careful comparison, and 

 original views. It is the work of Dr. Karl Ernst von Baer, and is enti- 

 tled, " Beitrage zur kenttniss der niedem Thiere," being, however, 

 chiefly devoted to the class, or rather, according to the principles laid 



