Miscellaneous. 265 
longitudinal vessels, situated near the plane of horizontal symmetry 
of the intestine e, springs a vascular branch, which sometimes bifur- 
cates and opens into the ventral vessel, so that the blood starting 
from the dorsal vessel is obliged to traverse the whole network be- 
fore entering the ventral vessel. 
ese arrangements are partly ES by the hepatic cells in the 
living animal. They seem to indicate that the intestine of the 
Naides, which is clothed with vibratile cilia, plays an important part 
in respiration. 
e ventral vessel is prolonged to the posterior extremity of the 
caudal lobe. There it bifureates, giving origin to two branches, 
which run along the margins of the triangular lobe, cutting off at 
its lateral angles two equilatera al triangles. rom each of these 
branches, opposite to each respiratory digitation, springs a branchlet 
which penetrates to the apex of the digi tation, where it is recurved 
in a loop, and is then connected with the vascular loop of the digita- 
lion of the same side. From this two lateral vessels are produced, 
which unite with the prolongation of the two parent branches to 
form the dorsal vesse 
Suppressing the special contrivance of the respiratory lobe of Dero 
we arrive at the type of the vascular apparatus of Wais proper.— 
Comptes Rendus, June 6, 1870, tome lxx. pp. 1226-1228. 
Observations on the Natural ew of the Crayjish. 
By M. Cua 
Copulation.—The copulation of "sh ee takes place during a 
period which includes the months of November, December, and 
January. The male seizes the erste with his large nippers, turns 
her over, and En he holds her lying on her back, places himself 
in such a manner as to pour out the fecundating material upon the 
two outer lamelle of the tail. After this first operation, which lasts 
some minutes, he conveys her rapidly beneath his abdomen in order 
to effect a second deposition of semen upon the plastron round the 
external opening of the oviducts, by means of the curious mechanism 
80 esl described by M. Coste. 
Oviposition.— According to the degree of maturity of the ova at 
the time of the union of the sexes, oviposition takes place at a apo 
varying from two to forty-five days after copulation. At the 
upon her back and brings up her tail upon her plastron, in such a 
manner as to form with her abdomen a chamber enclosing the aper- 
ture of the oviducts, and the wall of which secretes a viscous fluid 
intended to fasten the eggs to the abdominal appendages during in- 
cubation. When things are in this state, the laying of the eggs 
takes place. It is effected at once, usually during the night, rarely 
during the day. Incubation lasts yen six months ; and the hatch- 
ing takes place in May, June, or Jul 
Moults.—The first moult takes dites ten days after exclusion; 
the second, third, fourth, and fifth at intervals of from twenty to 
