32 Moll . 
MOLLUSCA. 
The rostrum grew by apposition, and its form was determined by the 
phragmocone. 3. The pro-ostracum was covered by the anterior portion 
of the rostrum ; this part was not sharply marked off from the rest. 4. 
Like the rostrum, the phragmocone had a thin calcareous margin, which 
projected beyond the rostrum, and in the dorsal portion of which the 
pro-ostracum lay. 5. In the Sepia sholl all characteristic components of 
the Relemnite shell are to bo found ; the sipho alone lacking ; Riefstaiil. 
Researches on myohae matin and histohaematins ; MacMunn (2). 
3 . Digestive System. 
Digestive organs of Buliminus sp., described by Simroth ; Bcettger, 
(11) pp. 17-20. 
The radula of 5 genera of Stylomatophora is elaborately described and 
figured by Dybowski, (1) ; his conclusions are summed up as follows : — 
I. The inner lateral plate provided with a median lateral tooth. 
a. The outer lateral plates are hook-shaped, very long, and with 
a cutting* edge along their whole length : Limax , Hyalina. 
b. The outer lateral plates are hook-shaped, short, and have a 
toothed margin : Vitrina. 
II. The inner lateral plates have no lateral tooth. 
The outer lateral plates have long pedicles : Succinea. 
b. The outer lateral plates are lamellar and toothed on the 
posterior margin : Helix , Avion. 
Dybowski (2) in attempting to answer the question as to the syste- 
matic value of the radula, gives some preliminary communications, with 
an account of his modes of observation and delineation, with special 
descriptions and detailed measurements in the case of Amphipeplea and 
Planorbis. 
The oral lobes have been investigated in eighteen families of Pelecy- 
poda , and in several forms .their anatomy examined. They are covered 
with a single layer of ciliated epithelium, beneath which there are goblet 
cells. Cells, apparently sensory, are also found in grooves or on eleva- 
tions of the epithelium. In Mytilus , a large blood-space runs along the 
upper edge of the oral lobe, which may be regarded as a true vessel homo- 
logous with the tentacular artery of the Naiadce. Below the sub-epithe- 
lial basemeut membrane are muscles and nerves, disposed parallel to the 
long axis of the organ. At the lower margin are a number of cells, 
probably glandular, though their ducts have not yet been demonstrated ; 
aud along the junction of the ridges with the tegumentary fold are 
structures apparently corresponding with the chitinous rods in the gills. 
Direct experiments have shown the lobes to have an ingestive function, 
though the marginal cilia produce a current seemingly intended to drive 
away the water from which food has already been obtained ; perhaps 
there is also a secondary respiratory function ; Thiele. 
4. Circulatory System. 
The blood-passages of Pelecypoda , even the so-called “ arteries,” are all 
lacunae, and the muscle-fibres which surround them are not proper to 
