Mr Gulland on the Sense of Touch in Astacus. 151 

 Explanation of Plate. 



Fig. 1. Ova of Lcpadofjastcr Decanclolii (Day), attached to piece of slate ; 

 natural size. 



Fig. 2. Ovum of same fish, fourth day after fertilization ; a, oil globule ; 

 magnified. 



Fig. 3. Thirteen days after fertilization, blood circulating, and somites 

 visible. 



Fig. 4. Young fish, hatched 14th July, sketched 26th July, 1885 ; length, 

 ^ inch. 



Fig. 5. Same stage, magnified. 



Fig. 6. Ventral surface sixteen days after hatching. 



Fig. 7. The ventral sucker of the mature fish. 



Fig. 8. Sucker of young Cyclopterus limvpus, 1 inch in length. 



Fig. 9. Sucker of Gohius formed from ventral fins. 



Fig. 10. Sucker of Liigaris Montagui. 



X. The Sense of Touch in Astacus. By G. Lovell Gulland, 

 Esq., M.A., B.Sc, M.B., CM. [Plates VIII. and IX.] 



(Read 16th December 1885.) 



Inteoduction. 



The following is an account of the principal papers in 

 which the sense of touch in the Crustacea and allied forms 

 has been discussed. 



The latest writer (if we except the ordinary text-books) 

 who approaches the subject of the sense of touch in Astacus y 

 or indeed in any of the higher Crustacea, is Huxley, who ^ 

 suggests that the " setse, so generally scattered over the body 

 and appendages, are delicate tactile organs ; " and then goes 

 on to point out the likelihood that they are in some way 

 connected with nerves. We shall see how this opinion has 

 arisen. 



De Morgan 2 sums up the literature of the subject up to 

 his time, and suggests that the tufts of bristles on the large 

 claw of the lobster are tactile in function. He traces the 

 nerve-fibres to a point near the bases of the setae in the 

 " flabellum " of the tail of the prawn and propodite of the 

 claw of the shrimp, but makes the mistake of supposing that 



1 The Crayfish, p. 113. 



2 On the Structure and Functions of the Hairs of the Crustacea, Phil. 

 Trans., 1858. 



