618 CLASS X. 
lobster. In the hermit-crab (Pagurus) there are, besides the cephalic 
ganglion, only six ganglia, but the form of the nervous system is 
in other respects the same’. 
The nervous system existing especially for the organic life, 
which we have already noticed in insects and spiders, is not want- 
ing in the crustaceans also, however it still in many families 
remains for the most part or entirely unknown. It has been 
especially investigated by BranpT in some Decapods, Stomapods 
and Oniscides. In crays and in Squilla it consists of a single 
portion and two lateral portions. The single portion arises at the 
posterior margin of the cerebral ganglion, and has no nervous 
ganglion that lies in front of the brain as in insects; the lateral 
portions arise from the cesophageal band that connects the cerebral 
ganglion with the succeeding ganglionic cord. Distinct ganglia are 
not present at the origin of the lateral portions, but appear to 
be fused with the cesophageal band, which indicates a swelling at 
the point of origin of these lateral nerves. The system of nerves 
spreads itself over the stomach, presents here one or two ganglia, 
and finally divides into two branches which are distributed to the 
liver. In Porcellio BRANpr? found no single portion of this system, 
but only two small lateral swellings, situated behind the cerebral 
ganglion and connected to it by two thin filaments, which send fine 
branches backwards to the stomach?. 
In most crustaceans, common feeling on account of the hardness 
of the covering cannot be otherwise than very small. The antenne, 
which are often much developed and four in number, are wanting 
only in-few, and, like the whiskers in mammals, may serve for a fine 
sense of touch even in the dark. In like manner, probably, the 
jointed filaments of the cirripedia, and the filaments on the foot- 
jaws of the decapods and other appendages of the body, may serve 
for touch in many species. <A special organ for taste is not known, 
but the seat of this sense appears to be in the commencement of the 
cesophagus %. 
1 SwamMMERDAM Bibel der Natuur. bl. 204—206, Tab. x1. fig. Ix.; comp. also 
Owen, Catalogue of the physiol. Series of the Museum of the Coll. of Surgeons, Iv. 
pp. 16, 17, who in other species of the same genus found only four ganglia besides the 
cerebral ganglion. 
2 Comp. BRANDT in his Bemerkungen iiber die Hingeweidenerven der Evertebraten, 
cited above (p. 279). 
3 According to MILNE Epwarbs, who appeals to his observations made with 
