7 Grufit. 
CRUSTACEA. 
Jobert [op. cit. xiv. Crust p. 16], and Semper [supral^, relates some 
experiments made by himself upon Carcinus mcenas (L.), which often 
spontaneously leaves the sea water. When confined to sea water with- 
out renewal of oxygen, it lifts up its forepart above the water and takes 
air into the gill-cavity through the openings near the mouth, by which 
ordinarily the respiratory water is expelled, and this air leaves the cavity 
through the orifices at the base of the first pair of feet, by which ordi- 
narily the respiratory water is taken in ; the mechanical course of the 
movement is given by the inward appendage of the second maxilla. The 
same mode of respiration also takes place when the whole animal is out 
of the water. Kept immersed under water without renewal, these crabs 
seldom live longer than one or two weeks ; but when enabled to breathe 
air, as above mentioned, they can live for two or three months. Kept 
without water in damp air, they can live more than 5-8 days ; and if put 
into water every third or fourth day for a quarter of an hour, in order to 
moisten the gills, they survive for two or three weeks. As it has been 
proved by physiologists that in normal respiration the quantity of con- 
sumed oxygen is greater than that of the expirated carbonic acid, but 
that in dyspnoea both quantities are nearly equal, the author has measured 
both constituents in the air-breathing crab ; and, having found the quan- 
tity of carbonic acid much the lesser (54-76 per cent.), concludes that 
this air-breathing may be regarded as normal, and equivalent to the 
aquatic respiration. 
In the paper by F. Jolyet & P. Regnard, “ Sur la respiration des 
animaux aquatiques,” Arch. Physiol. (2) iv. [1877], pp. 44-62, & 684-633, 
experiments on the respiration of several Decapod Crustaceans are also 
related. 
Leidy has observed Ocypode arenaria (Say) to survive in good condi- 
tion for eight daj^s, without once having been in water. P. Ac. Philad. 
1878, p. 337. 
Nervous System and Organs of Sense. 
Histological and morphological notes on the central ganglion of the 
common crayfish, by R. Krieger, Zool. Anz. i. pp. 340-342. 
G. Bellonci describes the microscopical structure of the central 
ganglia in Squilla mantis. He distinguishes small, middle-sized, and 
large cells. The first are the most important ; they have only a very 
thin protoplasmatic envelope round their nucleus, are situated chiefly on 
the lateral protuberances of the cerebral ganglion, and seem to be emi- 
nently sensitive, “representing the centres of the psychical individuality.” 
All nerves originating from the median ganglia have two roots, an upper 
and an under one, as in the Vertehrata ; in those of the cerebral ganglion 
only, the upper one is sensitive and the under one motory, in the 
others this is reversed. The cerebral or supra- oesophageal ganglion is 
composed of three pairs of ganglionous masses, corresponding with the 
three segments of the head ; the anterior pair supplies the optic nerves, 
the middle the inner antennae, the posterior the outer antennae. Ann. 
Mus. Genov, xii. pp. 518-545, pis. iv.-x. ; a previous summary by the 
author in Rend. Acc. Bologn. 1878, pp. 88-96. 
