68 On the Morphology of the Echinoidea. 



besides the ability to excrete mucus, whilst the former are 

 mucus-secretors par excellence. 



It appears to me that the organs described by Dr. Ham arm 

 are modified pedicellarige. There appears to be great varia- 

 tion in the morphology of the mucus-secreting organs in the 

 Echinoidea, and whilst the organs described occur in numbers 

 in half grown Sphoer echini, they ap])ear to me to diminish in 

 numbers in larger forms. The name " globiferi " is unfortu- 

 nate, for so many echinodermatists follow U. F. Miiller, 

 and term the long-stalked and big-headed pedicellarite ^j- 

 glolnferce. 



In order to prevent confusion, as the ground is occupied, it 

 would be as well if Dr. Hamann would alter the name of the 

 interesting organs he has discovered, 



II. The Termination of Nerves in the Echinoidea. 



Having been practically interested in this subject, and 

 having traced the ending of nerve-fibres in the tentacles of 

 some Ecliinida, it was necessary to recognize the work of 

 former observers. In the midst of my work I had the oppor- 

 tunity of verifying Sladen's statements {op. cit. p. 107, and 

 pi. xiii. fig. 12) and of examining his microscopic preparations. 

 He stated with regard to the tactile cushions on the inner 

 surface of the calcareous valves of the pedicellariee globit'erai : 

 " These organs, which are finely papillate and richly supplied 

 with nerve-fibres (as will be found indicated in the section in 

 pi. xiii. fig. 12), are presumably of sensorial (?'. e. tactile) func- 

 tion, and act as the communicators of the advent of any foreign 

 or irritating elements." The drawing shows, what can be 

 well seen in the thin section, a number of j)arallel nerve-fibres 

 coming to the surface from out of a layer of nucleated cells. 

 The surface has a very delicate flat epithelium raised here 

 and there into setiform projections. The drawing speaks for 

 itself, and the similarity of the structures represented and 

 those which were described and ligured some years afterwards 

 by Sven Lov^n is remarkable. I have seen the same struc- 

 ture in Coelopleurus Maillardi and cannot consider the draw- 

 ing otherwise than correct. 



Lov^n, in his wonderful work on the genus Pourtalesia 

 (' Kongl. Svenska Vetenskaps-Akademiens Handlingar,'' 

 Bd. xix. no. 7, 1883, pp. 45 to 55, pi. ix.), described and 

 figured, with his usual great accuracy and art, the terminations 

 of the pedicel-nei ves. In fig. 82 the sette and the expanded 

 nervous structure at the tip of the fibre are distinct, and in 

 figs. 86, 87, 89, and 90 the relation of the nerves to the sur- 



