G. GENERAL NATURAL HISTORY AND ZOOLOGY. 299 



"splint" bone on those in front, was also found, thus form- 

 ing an interesting miocene link in the genealogy of the horse. 

 Over thirty species of fossil horses were found ; as also a 

 species of rhinoceros, camels, suillines, and other large mam- 

 mals, etc. 4 2>, July^ 1876. 



HABITS OF AMERICAN FRESH-WATER RHIZOPODS. 



Professor Leidy, in continuation of his studies on our 

 American fresh-water Rhizopods, describes the habits of 

 the genus Hyalosplimnia^ the shell of which is homogene- 

 ous and transparent. Several species have been described, 

 one of which was discovered in the sphagnum swamps of 

 New Jersey, and from its resemblance to a butterfly, w^hen 

 the pseudopods or arms are extended, it has been named 

 Ilyalosphmnia papilio. Pores were found to exist in the 

 shell, through which the \vater passes in and out as the 

 body dilates and contracts. Foreign substances adhere to 

 the naked Amoebce on the part of the body opposite to that 

 from whence the pseudopods are protruded. A sluggish 

 Amoeba had been observed to swallow shelled Rhizopods^ 

 and, after digesting the soft parts, the shell was ejected. 

 Others had been observed to select specimens of diatoms 

 having green digestible matter in their interior from those 

 which were not possessed of such nutritive material. 



MIGRATIONS OF THE LEMMING. 



The remarkable migrations of the lemming in Norway 

 have long excited the wonder of observers ; the precise im- 

 pulse which induces this diminutive rat to take up this jour- 

 ney, always in a definite direction, being a problem of very 

 difficult solution. Mr. Duppa Crotch has propounded a new 

 view in explanation, w'hich is ingenious, if not entitled to con- 

 sideration. As is well known, these animals always move 

 westward in their migrations, and finally, in diminished num- 

 bers, perish in the sea. In one instance a ship is said to have 

 sailed for fifteen minutes through an army of tliem, the water 

 being literally covered as far as the eye could reach. Ac- 

 cording to Mr. Crotch, this migratory instinct is hereditary 

 from progenitors that in. a past geological age dwelt in an 

 island of plenty now submerged beneath the Atlantic. Al- 

 though tliere is now no land to be reached, and the goal act- 



