1881. ]. Recent Mollusca during the year 188o. 709 
A synopsis of a lecture, by Professor A. Hyatt, given before 
the American Association, appears in the Naruratist for De- 
cember (p. 915-6); the subject being the transformation of Plan- 
oris, as a practical illustration of the evolution of species. Al- 
though based on the study of the fossil forms of Steinheim, it is 
referred to here on account of its obvious bearing on the general 
subject. 
A fully illustrated memoir on this subject is contained in the 
memorial volume of the Boston Society of Natural History. 
In the Naruratist (March, 1880), p. 207, Mr. R. Ellsworth 
Call has a note on reversed specimens of MMelantho (Campeloma), 
and an examination of embryonic shells of several species, show- 
ing that from fifteen to twenty-five reversed specimens were found 
in every thousand, of which, however, it is believed by Mr. Call, 
only one-tenth per cent. survive to maturity. He suggests that 
the reversals may be due, as some other irregularities are, to 
crowding in the ovarian sac. 
A circular has been issued by Messrs. R. E, Call and A. F. 
Gray, asking the cooperation of conchologists in providing mate- 
rial for a proposed monograph of the Unionide of North America, in 
which they propose to figure the anatomy of each species in detail. 
The polymorphous forms of Axodonta found in the United 
States, are referred to in a note by Professor Call in the Natu- 
RALIsT for July, p. 529. The existence, everywhere about us, of 
transition forms of animals, is now being generally recognized by 
naturalists, who formerly, under the blinding influence of the 
dogma of fixity in specific characters, wandered hopelessly from 
the extreme of naming every individual variation, to that of con- 
founding every sort of minor characteristic under one specific — 
name. Now that a certain amount of freedom in these matters 
has become habitual, we may look for the speedy recognition of 
the particular effects produced by at léast the more simple features 
of the environment, of which several of our Western naturalists 
have already given us a foretaste. 
In the American Naturauist for July (p. 522), R. Bunker 
hotes that a specimen of Lymne@a elodes Say, from which a piece 
of shell the size of a half dime had been broken out, showed 
Signs of reparation in three days, and in six weeks the injury was 
completely repaired, the mollusk meanwhile iplitin sieved its usual 
functions in an aquarium. 
