ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
725 
aperture there is a thick white mass formed from numerous accessory 
tubules. A pair of large and remarkable glands with long efferent ducts 
opening at the sides of the mouth, are described provisionally as 
spinning glands. The reproductive organs are like those of Vaginula ; 
the female genital aperture is beside the anus and pulmonary aperture ; 
the vas deferens extends forwards under the epidermis ; the penis has 
no accessory gland. The oesophageal ring is very narrow. The whole 
of the interior is without pigment; the external pigmentation varies 
even within the limits of one species. Shell and shell-sac are as com- 
pletely unrepresented as in Vaginula. Dr. Simroth describes the 
minute anatomy of the organs, and then compares the three genera 
Onchidium, Vaginula , and Atopos , which he regards as links of one 
genetic chain. 
Development of Liver of Nudibranchs.* — M. H. Fischer has made 
a study of the young of Eolis exigua. When the larvae escape the 
digestive tube is composed of a moderately long oesophagus, an ovoid 
stomach, and an intestine. In the anterior region of the stomach organs 
lie to the right and left ; that on the left is a sac of some size, the cavity 
of which opens into the digestive tube and is lined by large cells with 
very fine cilia ; these cells are capable of intracellular digestion, and the 
sac is the active digestive organ of the larva. The organ on the right is 
very small, and appears to have no function. The two form respec- 
tively the right and left lobes of the liver ; the larval stomach has no 
relation to the similarly-named part in the adult. The two lateral 
organs increase in size, and in time the right hepatic lobe gives off a bud 
which goes to the right dorsal papilla and the left one which goes to the 
left, while behind it are a pair of buds destined for the second pair of 
papillae. The liver of the adult Dorid is composed of a principal and of 
an accessory mass which seem to be derived respectively from the right 
and left lobes of the embryo. 
Integument of Chiton.f — Herr J. Blumrich describes the structure 
of the decalcified dorsal shells of Chiton siculus, Ch. laevis , Ch. Polii , 
and Acanthochiton fascicularis, the disposition, arrangement, and develop- 
ment of the aesthetes and their fibrous strands, the mantle margin and 
its spines, and finally the epithelium of the branchial groove, the 
smelling organ, and the foot. The ectodermic epithelium in Chitonidae 
typically consists of two kinds of cells, thread-like and glandular, with 
a simple cuticular fringe. This type is seen in the epithelium of the 
sole and in the glandular epithelium of the wall of the foot and of 
the olfactory organ. On the mantle- wall of the branchial cavity, the 
epithelium consists of cubical ciliated cells and is only locally glandular. 
The epithelium of the mantle is most divergent, for its cells have a 
very strong cuticular covering. This may be chitinous as in the 
“cuticula” and the “tegmentum,” or calcareous as in the “ articula- 
mentum ” and the spines. The glandular cells on the mantle are 
mainly restricted to the aesthetes and to most of the spine-bearing 
papillae. There is no real difference between cuticula and tegmentum, 
the latter being simply the cuticula continued over the articulamentum. 
* Arch. f. Naturgesch., lvii. (1891) pp. 75-104 (5 pis.) 
t Zeitschr. f. Wiss. Zool., lii. (1891) pp. 404-76 (8 pis. and 1 fig.). 
