154 THE AMERICAN NATURALIST. [VoL. XXXIV. 
The pericardial glands of lamellibranchs manifest three different 
types: intra-auricular masses in Pecten and Ostrea, external epithe- 
lium of the auricles (Mytilus), tubular glands opening virtually into 
the pericardium (Naiades). Pecten maximus affords a clear transi- 
tion from the type of the lamellibranchs to that of the gastropods 
in that the connective tissue encloses, as in the latter, many isolated 
cells, which are massed in the wall of the auricles. The products in 
the cells of the pericardial glands of either type are engulfed by 
phagocytes, which transport them into lacunæ of the circulatory sys- 
tem. Some of these phagocytes reach the exterior through the bran- 
chial membrane; the others become fixed for life in the connective 
tissue. 
In the cephalopods the excretory connective-tissue cells are accu- 
mulated exclusively in the wall of the branchial heart and of the 
appendix to that organ. In both organs, however, cells of a differ- 
ent character are present. In various gastropods (Pulmonata, Opis- 
thobranchiata, and some Prosobranchiata, as Cyclostoma) the liver 
contains numbers of excretory cells which discharge their products 
into the intestine. 
The collaboration of closed excretory cells and phagocytes to 
eliminate waste products, or at least to localize them in indifferent 
regions, is found in many groups : Oligocheta, Polychzta, Hirudinea, 
Sipunculida, Echinoderma. This method of excretion, which encum- 
bers the tissue with masses of solid granules increasing with age, is 
evidently an imperfect function, and not improbably contributes to 
determine the death of the individual. Hinh Wisb 
The Heart of Anodonta. — The action of the heart of Anodonta 
has been fully studied by V. Willem.! Under ordinary circumstances 
the heart beats four to six times per minute. Contraction can be 
induced in an empty, quiet heart by injecting fluid into it, but an 
overfilling of the heart will retard the rate of contraction. The 
contraction of the ventricle drives the blood out under a pressure of 
one to three and a half centimeters of water. When the ventricle 
contracts, the auricles expand, and together these organs always fill 
the whole pericardial space. The contraction of the ventricle acts as 
a suction pump on the blood in the gills, drawing it into the auricles, 
. and as a force pump on the blood in the arteries. G. HP. 
1 Willem, V. Recherches expérimentales sur la circulation sanguine chez 
l'Anadonte, Mem. couron. Acad. Roy. des Sciences, des Lettres, et des Beaux-Artes 
de Belgique, tome lvii, 28 pp., 2 pls., 1899 
