540 General Notes. 
until it reaches the opposite shore, it will stop for a few moments 
and exhale the air which is held down by the ice. Interchange of 
gases takes place between the air and water, when the animal re- 
breathes the air and makes another start, repeating the act until the 
shore is reached. I do not claim this as an original observation ; 
others than myself have noticed it. It is well known by those who 
have observed the phenomenon that if the ice is struck immediately 
above the air, and the air thus scattered into numerous bubbles, the 
muskrat drowns. Having noticed an account by Professor Com- 
stock of the use, by the “ water boatman ” of a bubble of air for a 
tracheal gill,! I would call attention to this interesting feature in 
the physiology of respiration of the muskrat.— W. L. Spoon, Univ. 
N. C., May 1, 1888. 
ZOOLOGICAL News.—CaLENTERATES.—Dr. G. Hubert Fowler, 
in the fourth part of his papers on the anatomy of the Madrepora- 
ria (Q. J. Ms., 1888) discusses the structure and systematic positions 
of the genera Madracis, Amphihelia, Stephanophyllia, Stephanotro- 
chus, Stephanaria, Pocillopora and Seriatopora. e points made 
are mostly of minor importance, except that certain cells described 
as coral-forming (calycoblastic) cells, occurring in several genera 
really function to hold the mesenteries more firmly to the corallum. 
ECHINODERMATA. — The number of species of Asteroids col- 
lectd by the French scientific expedition to Cape Horn is thirty- 
eight, twenty-three of which are new, while thirty-two were not 
represented in the museum of the Jardin des Plantes. The num- 
ber of species known from the southern point of the American con- 
tinent now reaches fifty-seven. M. E. Perrier finds great variabil- 
ity in each species, correlated with the varying conditions under 
which they exist. 
Wor{s.—Beddard describes (Quart. Jour. Micro. Sci., 1888) the 
anatomy of the earthworm Allurus tetraedrus, pointing out. the 
features in which this genus differs from Lumbricus and Allolobo- 
hora. 
MorLusca. — M. H. Fol, in a recent note on striated muscular 
tissue among the invertebrates, acknowledges that his statement, pe 
a previous communication, that true muscular tissue does n 
occur in any mollusc is erroneous, since such tissue forms à portion 
of the adductor muscle of Pecten. : iad 
M. H. de Lacaze-Duthiers, as a result of his extensive analy ei 
studies upon the netvous system of the Mollusca, proposes 4 a 
classification of the gasteropoda, based upon the differences 10 © 
structure of the nervous centres. 
1 Am, Nat., June, 1887. 
