ANATOMY AND PHYSIOLOGY. 
Moll. 5 
Anatomy and Physiology. 
The histological structure of the skin of the terrestrial and freshwater 
Gastropods is discussed by Leydig in a very elaborate paper, Arch. f. 
Nat. xlii. pp. 209-264, pis. ix.-xxvi. Yibratile cilia are found in the 
aquatic species nearly on all parts of the surface, with some exceptions ; 
in the terrestrial snails chiefly on the under side of the foot, but with 
certain intervals, and also near the mouth and respiratory orifice ; the 
epithelium of land-snails consists only of one layer of cells, some of which 
are open or cyathiform, and covered by a very fine cuticular stratum ; 
intercellular passages (channels) are found within the epithelium, and, 
perhaps give issue to the contents of the mucous and pigmental glands, 
the structure and distribution of which are carefully examined ; mucous 
glands are wanting in the parts of the animal always covered by the 
shell. The mucPus glands are not uniform in the same animal, some 
contain small spindle- or grindstone-shaped bodies, others are connected 
with the end of a nerve ; the “mucous pore” at the hinder end of the 
foot in Avion is composed of many distinct mucous glands, and may be 
compared with the byssal gland of some Bivalves. The pigmental 
glands pass by degrees into calcareous glands filled with a deposit 
of fine-grained calcareous matter ; these are most abundant in the edge 
of the mantle in the shell-bearing snails. Besides these glands, the 
corium of snails also exhibits distinct blood-vessels, though in small 
numbers ; it is chiefly composed of rather spongy supports of conjunc- 
tive tissue, the cavities between which communicate freely with those of 
the blood-vessels. The internal shell of Limax consists of a homo- 
geneous cuticle, which is more or less calcified, and is situated under the 
corium of the back, and above a cushion exhibiting microscopical rods 
and vibratile cilia ; this may, perhaps, be compared with the “ rosette- 
shaped” bodies of the Annelides, and be in near relation to the renal 
system ; but here the author is careful not to draw any final conclu- 
sions. The external shell of the land-snails is composed of (1) a homo- 
geneous cuticle, (2) a calcareous layer, and (3) a homogeneous lamella 
of colourless substance, and exhibits in most species a distinct micro- 
scopical sculpture outside, and in some also inside, which is described 
pp. 49-52, for some of the more common species. The author maintains 
his former assertion that the shell of the PectinihrancTiia is originally a 
secretion of the epithelium, whereas in the Pulmonata it takes its origin 
within the skin itself, and only afterwards becomes free. 
H. V. Ihering gives an account of the physiology and histology of 
the central nervous system of Helix pomatia. Abh. Ges. Getting, 
xxi. 
Kollmann has published several observations on the circulation in 
Bivalves, Cephalopods, and Aplysia. Tn the last, all arteries are, 
according to him, closed at the end ; the blood passes from them into 
the interstitial holes pr lacunas of the body, like the serum or lymph of 
the Vertebrates, and is pressed from thence to the gill ; true veins are 
altogether wanting. In the Bivalves, there are capillaries and veins, 
1870. [voL. xnr.] r 2 
