142 QUARTERLY CHRONICLE. 
scopic eyes have been much overlooked. They consist of a 
black or reddish pigment of very definite structure, impression- 
able by luminous rays, and in immediate relation to the 
nervous system in those animals which possess one. Photo- 
scopic eyes have been met with in the Sipunculidz, in certain 
Annelida,* and especially in the Hermelle, described by De 
Quatrefages. The photoscopic eyes of Asteracanthion have 
long been known as pigment spots situated at the end of each 
ray. They are, however, more fully organized, and more 
certainly visual organs than was once supposed. They occupy 
a small papilla near the end of each ray, in the interambulacral 
furrow, which receives a filament from the ambulacral 
nervous trunks, enlarged beneath into a ganglion. The 
spiniform calcareous processes surrounding this tubercle can 
be closed down upon it by muscles, thus forming a sort of 
eyelid. When placed under the microscope the oculiferous 
papilla is seen to consist of red pigment indented and covered 
over by a gelatinous medium of lenticular form, the whole 
being intimately connected with the nerve filaments. The 
gelatinous medium serves to concentrate the light, and it is 
considered by M. Jourdain that we have here the most per- 
fectly organized photoscopic eye. 
Observations on the Structure of the Nervous System in 
Clepsine. By E. Banpetor. (‘Comptes Rendus,’ Nov., 1864.) 
—The nervous chain of Clepsine is of the same type as that 
of the other Hirudinez. One of the ganglia examined shows 
two elements—the fibrous and the cellular. The fibrous por- 
tion appears as a median ribbon, the cellular consists of six 
capsular inflations, which appear to contain unipolar cells, 
varying in size from the >2,th to >4,th millim. Each of 
these contains a nucleus of large oval form, with enclosed 
nucleoli. The produced extremities of the cells are connected 
with radiating fibres. The various ganglia are found to be 
composed more or less pairs of simple ganglia, according 
as they contain more or less of the cellular capsules. Cells 
are attached also to very fine lateral branches, and a gastric 
system is ascertained to exist in Clepsine, showing that the 
gastric network detected by Faure in the leech is the analogue 
of the stomato-gastric of other annelids. 
A paper on ‘ The Development of some Opisthobranchs’ ap- 
peared last quarter, by Mr. Alexander Stuart, of St. Peters- 
burg, in which he traces the growth of the ovum, and its in- 
timate structure at various stages of development. A paper on 
the tissues of the Echinodermata is also published by the same 
author, in which he says that he has accurately ascertained 
* See Mr. Lankester’s paper on the Earthworm, p. 111.—Ep. 
