40 SUMMARY OF CURRENT RESEARCHES RELATING TO 



siphon and the nature of the light. The amplitude and the duration of 

 the contractions have a definite relation, which is constant with a light 

 of the same intensity at different distances. Lights of different colours 

 give different results. Further details are promised after the use of 

 a new recording apparatus. 



Movements of Detached Gills.* — Mr. D. Macalpine gives an account 

 of his observations on the movements of detached gills, mantle-lobes, 

 labial palps, and foot in bivalve Molluscs. He asserts that all of these 

 organs, when detached from the body, are capable of moving visibly and 

 at a measurable rate of speed. The movement may be either rotatory 

 or progressive. One labial palp was observed to make twenty-six revo- 

 lutions at an average rate of 8 J minutes per round. A palp of the fresh- 

 water mussel (TJnio) continued to rotate for eight days. The gills 

 travelled forward at the rate of two minutes to the inch. The move- 

 ment of the mantle-lobes is rotatory, but a certain amount of forward 

 movement occurs in the course of rotation. The foot, laid in sufficient 

 water to cover it, exhibited motion of both kinds. The rate of rotation 

 was a complete round in 6 hours 47 minutes, the average rate of pro- 

 gress 1 in. per hour. It retained its power of movement for at least 

 73 hours. " The gliding gill and the rotating palp, the moving 

 mantle-lobe and the creeping foot, show what a stock of vital energy 

 must be stored up in the soft-bodied mollusc imprisoned within the 

 walls of the shell." 



Development of Mytilus edulis.j — Prof. W. C. M'Intosh remarks 

 that in one part of the estuary of the Eden the older mussels are covered 

 with dense feathery masses of GonotJiyrsea, upon which the young 

 mussels settle as soon as they quit pelagic life. The young are then 

 from 1/71 to 1/21 in. ; some show three gill-papillse and others thirteen. 

 An almost inexhaustible stock of young mussels could thus be obtained 

 at an early stage for transporting to any fresh site. Young mussels 

 may often be observed fixing themselves on various sites well adapted 

 for aeration and food. It is not right to suppose that all the mussels 

 found on a ship's bottom have, since the last " cleaning," grown to a 

 given considerable size. Mr. Wilson (whose important report to the 

 Scotch Fishery Board has been overlooked by some recent writers on 

 the subject) has shown that mussels can leave their sites and fix them- 

 selves to new ones by a fresh secretion of bygsus. In France, indeed, 

 they are often artificia.lly torn off, 



Molluscoida, 

 58. Tunicata. 



Monograph of Fragaroides aurantiacum.| — M. C. Maurice has 

 attempted to fill a lacuna in our knowledge of the Tunicata by preparing 

 a monographic account of a species, a method universally recognized by 

 zoologists as of the greatest value in advancing research. The form 

 which he has selected lives in abundance at Villefranche-sur-mer, and 

 is allied to Giard's genus Fragariiim, of which Fragaroides may be 

 regarded as a sub-genus. In discussing the orientation of the form the 

 author points out that his terminology corresponds, so far as the right 



* Trans. Roy. Soc. Victoria, xxiv. (1888) pp. 139-49. 

 t Ann. and Mag. Nat. Hist., ii. (1888) pp. 467-9. 

 X Arch, de Biol., viii. (1888) pp. 205-495 (7 pis.), 



