ANATOMY AND PHYSIOLOGY. 
Moll. 87 
which consists of three principal portions — crop, gizzard, and stomach, 
each of which is provided with a special armature of hard parts ; Amau- 
drut (1). 
The nervous system in Achatina panthera and Bulimus fnnlci is de- 
scribed in detail ; the retractor muscles of the central ganglia, described 
by Sicard in Zonites , are probably nerves. In Vaginula there is, properly 
speaking, no sub-cerebral commissure, but there is a filament similar to 
that called “labial commissure ” in Limncea ; the visceral chain consists of 
five (possibly six) ganglia, which furnish an argument against v. Jhoring’s 
classification of Vaginula along with OnchicUum ; Amaudrut (3). 
The nerves of the heart in Helix pomatia are non-medullated, but have 
a nucleated sheath. There are two trunks, the larger of which forms a 
plexus, while the smaller forms a small ganglion of seven or eight cells, 
and then ramifies in the ventricle. The muscles are accompanied by 
nerve-fibres throughout their whole length ; Tramrustj. 
In the nervous system of Cardium edule the results of Duvernoy have 
been confirmed and extended by Drost (1). Four kinds of sensory 
epithelium were observed : (1) pigmented epithelium sensitive to light ; 
(2) long-haired cells embedded in a depression of the cirrus-point ; (3) 
penicillate cells with short hairs ; (4) broad brush-cells projecting through 
cuticular warts. A distinct hyaline layer is found everywhere below the 
epithelium of the siphons ; their main mass is composed of longitudinal 
and circular muscles, but there are other fibres at right angles to both 
these, and two delicate layers just below the epithelium. Bottle-shaped 
pigmented glands occur in patches at the upper end of both siphons. 
Two other forms of glands are described; one bottle-shaped on the 
mantle-margin and below tho ciliated epithelium ; the other also on the 
mantle-margin, as well as on tho parts covorod by the young epicuticula 
or the shell. The author agrees with Flemming’s views on the nature of 
connective tissue. 
8 . Organs of Sense. 
Patticn (2) has made the eyes of Molluscs the subject of an elaborate 
memoir. (I) In Area there are three forms : (1) facetted, aggregated, 
and placed anteriorly and posteriorly on the mantle edge ; (2) inVaginate, 
on the mantle below the opening in the shell through which the byssus 
projects ; (3) pseudolenticulate, occurring irregularly among the invagi- 
nate forms. Each individual has about 1300 eyes. The compound 
(facetted) consist of 10-80 “ ommatidia,” each of which is wedge-shape 
and has a central core of two fused retinophorm and a double refractile 
rod or perceptive element. These arc surrounded by two rows of pig- 
mented retinuloe,” each having a homogeneous cuticula on its outer 
extremity. The nerve-fibres are connected in a manner described with 
the pigment cells and with the retinophorse. The invaginate eyes are 
thickened portions of the hypodermis, but have the same essential 
elements as those just described. The pseudo-lenticulate eyes are transi- 
tional, forming definite groups of non-invaginate ommatidia, with a 
prominent lenticular thickening of the cuticle. (II) In Pecten the forma- 
tion of images by the lens has been observed and is described. Some 
