336 Miscellaneous. 
shows nevertheless that the part interpreted by Vogt (1. c. p. 242, 
fig. 18) as a coracoid is really a portion of the matrix, so that the 
structure of the shoulder-girdle, so far as it is preserved, can only 
be ascertained after this has been removed. ll the inferences 
drawn from this part as to the relations of Archwopteryx to Birds 
and Reptiles therefore fall to the ground.—Sitzungsb. Akad, Wiss, 
Berlin, July 27, 1882, p. 817. 
On the Innervation of the Mantle of some Lamellibranchiate 
Mollusca. By M. L. Vratteton. 
The author has investigated the distribution and termination of 
the nerves in the part of the mantle lining the interior of the shell 
within the pallial line and the adductor muscles in the genera Unio 
and Anodonta. The process adopted was as follows :—The mantle, 
detached from its adherences in the living animal, was placed for 
fifteen minutes in lemon-juice, then in a 1-per-cent. solution of 
chloride of gold, where it was left for at least twenty minutes. It 
was then put into water acidulated with acetic acid (one drop to 
20 gr.), when the reduction is effected in from twenty-four to thirty- 
six hours. Fragments of the mantle carefully torn can then be 
examined ; or transverse sections can be made of it after hardening. 
The portion of the mantle within the pallial line is formed by a 
- lamina of connective tissue, rich in vessels and nerves, and covered 
on both surfaces with an epithelium of one layer-of cells. Trans- 
verse sections show that the nerves are not equally distributed in 
the connective lamina, but more especially in two planes near its 
two surfaces ; some are even placed immediately below the line of 
implantation of the epithelial cells. In a fragment containing one of 
these planes examined flat, the fibres are seen sometimes to fork or 
anastomose in the form of the letter Y, sometimes to cross at the 
same point, and their elementary fibrille form a tangle in which 
more or less complicated chiasmata are distinguished. 
The fibres thus constitute an irregular network, with nodal points 
of very variable form. The arrangement occurs on both surfaces 
of the mantle; but the two planes communicate by fibres situated 
in the thickness of the connective lamina, and really form only a 
single plexus. 
Each superficial plexus gives off finer fibres, which either originate 
directly from the large nerves of the plexus or, after the exhaustion 
of the latter, by repeated ramifications. These fibres finally divide 
into unifibrillar elements, which unite and anastomose in a thousand 
ways to form a plexus with very close meshes. It is subepithelial, 
for it persists when the epithelium is removed, but is more super- 
ficial than the one from which it originates. 
Thus in the mantle of Unio and Anodonta the nerves form a 
plexus perfectly analogous to that seated in the connective tissue of 
the cornea beneath Bowman’s lamina. It forms a very delicate 
nervous apparatus, which, being closely applied to the interior of 
the shell, may receive any shocks communicated to the latter, and 
transmit the impression of them to the animal. This arrangement 
is probably general among the Lamellibranchiata.— Comptes Rendus, 
September 4, 1882, p. 461. 
