Mr G'ldland on the Sense of Touch in Astacus. 175 



would have found that they invariably possess a lumen. 

 Their appearance so closely corresponds with Braun's own 

 figure {loc. cit., Taf VIII., Fig. 5) of a salivary gland from 

 the SBSophagus, that I refrain from drawing them. 



There are usually two lobes, sometimes, however, four or 

 more, and the lumina of the ductules converge to a point, 

 usually about the middle of the body, where they fall into a 

 common duct, which, piercing the superjacent connective 

 tissue and integument, opens on the external surface of the 

 claw. At the point where the main duct arises there are 

 generally two or three large nuclei different in appearance 

 to those of the proper cells, but of whose nature I am not 

 certain. They probably have formed the duct, and now re- 

 main as part of its wall. The form of these proper cells is 

 as Braun describes it, and the part nearest the lumen is 

 usually full of strongly refracting granules. From the above 

 facts, and since, moreover, these bodies are surrounded by 

 blood-sinuses — as indeed all actively functional parts in the 

 crayfish are — I consider myself entitled to regard them as 

 glandular, though what is the nature of their secretion or 

 excretion I cannot venture even to conjecture. 



It may be noticed here that Glaus ^ describes, in the thoracic 

 appendages of Phronima, glands opening to the exterior, and 

 precisely similar to the salivary glands, which he also figures. 

 Though these are much simpler than the glands in Astacus, 

 they are yet very like them ; they have the same kind of 

 duct and the same nuclei at the root of the duct. The main 

 difference is that in Phronima the ductules are intra-cellular, 

 in Astacus inter-cellular. Glaus suggests that these glands 

 in the legs secrete saliva, or something like it, which is 

 mixed with the food before actual ingestion; but I think 

 that this must at present be left undecided. 



Ganglion of the Great Claw. — With regard to the ganglion 

 on the nerve running to the claw, I was for some time of the 

 opinion that it might possibly be a reflex centre for the 

 closing of the pincers, and that nerve-fibres might pass from 

 it to the great flexor or adductor muscle of the dactylo- 



^ Der Organismus der Phronimiden, Arbeiten a, d. Zool. lust. Wien II., 

 1879, pp. 17-23, figs. 11, 16, etc. 



