1884.] Zoology. | 939 
greater number between the commissure and the hypodermis, 
often intimately connecting these two parts. 
The otocysts are spherical. The diameter of their cavity is 
w millim., and that of the sphere formed by the outer capsule 2, 
millim. The thick walls consist of a layer of fusiform cells, a net- 
work of fibrillæ arranged in a dense plexus, and a connective 
envelope. The cells form the greater part of its thickness; they 
are very delicate, spindle-shaped, slightly inflated towards the 
middle, where the nucleus is situated ; they also increase in thick- 
ness towards their inner extremity, where they are surmounted by 
a thick plate. The plates of all the cells are closely soldered to- 
gether, forming a cuticle, which, in sections, is often detached 
from the cells which produced it. No layer of vibratile cilia was 
to be seen distinctly, but indications ef them seemed to exist 
upon. portions which had been long in osmic acid. The cells 
taper at their base and at the same time bend in different direc- ` 
tions; and these basal prolongations anastomose and form a very 
delicate network of fibrilla, which, by their union, constitute at 
the base of the epithelial layer a regular little zone, intermediate 
between the nerve-fibers and the foot of the cells; a few nuclei 
are distinguishable in it, This plexus rests against the connective 
envelope, which is formed by a thin and dense membrane, pre- 
senting perforations through which the basilar plexus enters into 
oo with the nerve-fibers.— Comptes Rendus, March 24, 1884, 
757+ 
following two principal remarks: 
I. The animals which are truly pelagic from their birth to their 
death always swim freely in the water, never going either to the 
shore or to the bottom of the lake, and never touching the sur- 
€ of the water, so as to avoid coming directly in contact with 
the atmospheric air. 
2. The true pelagic animals carry their ova (with the exception 
of the winter egg) either attached to the exterior of the body or 
in a Sort of incubatory cavity until the young individual, whether 
‘mmediately like its mother or subject to transformation, can quit 
the envelope of the egg or the incubatory cavity, and lead at once 
the mode of existence of an accomplished swimmer. _ 
He author has studied the pelagic fauna of the following lakes: 
