SCIENTIFIC SUMMARY. 
401 
that certain species which in their immature condition resemble the tadpole 
of the frog, take on afterwards the typical character of the Cyprinodonts ; 
that certain apodal fish assume the structure of those which have pectoral 
fins ; and that some malacopterygii become in course of their development 
spiny-finned. Kecently he has discovered metamorphoses among members of 
the mackerel fanuly, and in these cases the changes undergone are more 
remarkable than those alluded to above. All ichthyologists are familiar 
with the generic character of the doree, which is termed Zeus faber, and 
with the morphological peculiarities which associate this animal with the 
mackerel group. There is another fish, less known to naturalists, Avhich 
inhabits the Mediterranean, and is termed Argyropelecus hemigymnus, and 
is supposed to be related to the Salmonidce. Now, there are hardly to be 
found two more distinct families than those of which the salmon and mackerel 
are representatives ; yet, marvellous to say, the Argyropelecus hemigymnus is 
nothing more than the young of Zeus faber. Agassiz admits that his asser- 
tion is a very startling one, but he calls upon zoologists to repeat his observa- 
tions, and he contends that his statements will be fully borne out. — Vide 
Comptes Rendus. 
External Auditory Hairs of Crustacea. — Herr Dr. Von Hensen has pub- 
lished a valuable memoir upon the auditory organs of decapod Crustacea, in 
which, among descriptions, he gives an account of the external hairs con- 
nected with the sense of hearing. These hairs are especially numerous in 
those species of the Carides which have no internal auditory organs. The 
hairs are situated upon the basal portion of the inner antennse, and on the 
second joint of the outer pair. They are found also on the tad. The cha- 
racters common to all forms of these auditory hairs are thus summed up ; — ■ 
(1.) They are always implanted over a hole in the chitinous membrane. (2.) 
The border of this hole is always elevated on one side into a sort of tooth. 
(3.) The stem of the hair does not rest directly upon the hole, but is sup- 
ported by a very delicate membrane, which is often dilated, so as to form a 
sort of ampulla at the base of the hair. This arrangement is calculated to 
isolate the hair from any agitation proceeding from the interior of the body, 
and at the same time, perhaps, to facilitate its vibrations. (4.) The stem of 
each auditory hair presents a sort of appendage, to "v^hich the nerve of the 
hair is attached. Properly speaking, the nerve terminates in a ganglion-ceU 
before it reaches the hair ; but from this cell arises a minute and slender 
nerve-cord, which enters the canal of the hair, and is attached to the stem 
appendage. The other superficial hairs do not exhibit similar complexities 
of structure, and, in particular, are wholly devoid of any nervous cord. — 
Vide Abstract of Dr. Hensen’s paper in Microscopical Journal, January. 
The Development of the Marine Crustacea, especially as concerns the larvae 
of Palinurus, has been carefully studied by M. Gerbe. He shows that the 
larva of the Palinurus of our seas does not resemble the typical Phyllosoma ; 
thus it does not present a trace of the false feet which are attached to the 
abdominal segments of Phyllosoma, the last of these segments being simple, 
instead of terminating with a fin composed of five laminas. But though at 
first it does not exhibit the character of Phyllosoma, M. Gerbe shov's that it 
does so after the fifth moult. He states that on witnessing the hatchings of 
the marine Crustacea, and following their development, we find that all make 
