30 PBOCEEDEJfGS OF THE 



APPE]!fDIX. 



Prof. Gr, B. Howes exhibited a specimen of Lima Tiians with a 

 byssus " nest " which it had spun in the jar in which it was 

 exhibited. The animal was obtained from the Zoological Station 

 in Naples, and he owed it to the generosity of his pupil Mr. G. 

 AY. Butler, who had been recencly working there. The indi- 

 vidual was one of three which came into Mr. Butler's hands, and 

 when placed in a glass vessel of sea-water, kept constantly re- 

 newed from an adjacent tank, they each constructed a byssus 

 enclosure. Upon removal from the last-named each constructed 

 a second "nest," and one prepared a third. Mr. Butler had 

 watched the animals both by day and by night, in vain, to ob- 

 serve the act of spinning. The period occupied in the construc- 

 tion of the enclosure exhibited was twenty-one days ; for the 

 first day or two only a few scattered threads were formed, but by 

 the fourteenth day the trabecular work, although thin, sufficed 

 to imprison its originator. The filaments composing the com- 

 pleted "nest" were attached between the side and the bottom 

 of the jar, which was a round one ; they passed for the most 

 part obliquely, and were interwoven in an irregular and complex 

 manner, giving rise to a kind of feltwork, which was densest at 

 its point of attachment to the side of the jar. The area en- 

 closed was a crescentic one bounded on its convex side by the 

 p-lass : the apices of the crescent nearly met, and the imprisoned 

 animal had secured free play over about two thirds the surface 

 area of the bottom of the jar. The animals were observed to 

 swim freely within their " nests " when completed. 



Professor P. Martin Duncans Exhibition. 



The two microscopic preparations exhibited this evening (see 

 p. i) demonstrate the fact that each ambulacral ampuUa in the 

 Echini is supplied by one offshoot from the main ambulacral 

 water-vessel. 



This fact was discovered by Gr. Valentin, and was recorded in 

 his ' Anatomic du genre Echinus,^ 1842, and the diagram given 

 in plate 7, fig. 136, of the work perfectly illustrated the meaning 

 of the author. 



This distribution of one vessel to each ampulla, supplying a 

 tentacle, has been accepted and taught as true by all subsequent 

 naturalists up to last year. 



Last year an able French naturalist, studying at the Lacaze- 

 Duthiers Marine Laboratory, not only stated that two vessels 

 supplied each ambulacrum, but drew, more or less diagramma- 

 tically, a representation of the results of his work. 



As I had never seen a second vessel coming off and entering 

 an ampulla, I asked our President whether he had had any ex- 

 perience in the matter. His suggestion was to count the number 

 of ampullae in a part of an ambulacrum, and also the number of 



