1881.) : Zobiogy. 657 
both the northern and southern tanks. Compared with Ascidians, 
Polyzoa are not very. generally distributed. Bugula is now the 
commonest, especially in the compartment for eels, where it 
flourishes along with Zoanthus and Hydractinia. Mullet and 
some other fishes, hurtful to various low growths, soon scour the 
rocks tenanted by Ascidians. 
e tank allotted to Annelids affords a spectacle of great 
beauty and variety; in short, it is a perfect microcosm. Of ‘its 
inhabitants, we can only note the young of a species of Spirorbis, 
a well known commensral of Palinurus. This annelid multiplies so 
fast that much trouble is spent in removing its tubes, shaped like 
a post-horn, which soon cement themselves with obstinate firm- 
ness to the glass windows of the aquarium. 
Fishes, if we except Selachians, do not breed well in the 
aquarium. Otherwise, they are flourishing prisoners; the condi- 
tions unfavorable to their -propagation have not yet been 
thoroughly ascertained. 
Tue Eve-Like OrGaNs oF THE SKIN OF CERTAIN FisHes.—M. 
Ussow, in the Bulletin of the Imperial Society of Naturalists of 
oscow, 1879, gives an account of these singular organs in 
Astronesthes, Argyroplicus, Chauliodus, Gonostoma, Maurolicus, 
He finds that in Astronesthes, Chauhodus 
Which the eyes are replaced by a large, probably luminiferous, 
®rgan which covers the entire frontal part of the top of the skull. 
Mason's Microscopic Sruptes in THE CentraL Nervous 
SYSTEM OF Reptices anp Barracuians.—A third article by Dr. 
John J. Mason on this subject, appears in the Journal of Nervous 
and Mental Disease for January, 1881. The author has studied 
the nuclei of the spinal cord of the alligator and Heloderma sus- 
sig cells of the central nervous system have, in the same indi- 
ae average diameters, which are proportional to the power 
“veloped in the related muscles.” 
