BIVALVULAR SWIMMERS. 137 



muscle enables them to do with great vigour.* When 

 deserted by the tide on any occasion, they will tumble for- 

 ward in this way until they have regained the water. Nay, 

 some popular writers repeat a story from the ancients, that 

 these scallops, by flapping their valves with a very quick 

 motion, can rise up from their beds in the deep, and navi- 

 gate the surface, having one valve raised and exposed with 

 its concavity to the breeze, while the other remains under 

 the water, and answers the purpose of a keel, by steadying 

 the animal, and preventing its being overset. What degree 

 of faith you are to place in this account I will not positively 

 say, but I think it probable that the sailing part of it is 

 an embellishment thrown in by way of effect, while there 

 can be no doubt of the Pectens' \dvacity, at least in its 

 early state of existence.-)" Our excellent friend the Rev. 

 David Landsborough writes thus : " We observed on a 

 sunny September day, in a pool of sea- water, left on Ste- 

 venston strand (Ayrshire) by the ebbing tide, what we at 

 first thought some of the scaly brood at play. On close 

 investigation, however, we found that it was the fry of 

 Pecten opercularis skipping quite nimbly through the pool. 

 Their motion was rapid and zigzag, very like that of ducks 

 in a sunny bhnk, rejoicing in the prospect of rain. They 

 seemed, by the sudden opening and closing of their valves, 

 to have the power of darting like an arrow through the 

 water. One jerk carried them some yards, and then by 

 another sudden jerk, they were off in a moment in a dif- 

 ferent tack. We doubt not, that when full-grown they 

 engage in similar amusements, though as Pectens of greater 

 gra\'ity, they choose to romp unseen, and play their gambols 

 in the deep."§ 



immissus vi elastica exsilit." — Faun. Groenl. p. 416. See also Arist. Hist. 

 Anim. 1. 4, cap. iv. 



" Les Limes volent, pour ainsi dire, dans I'eau par Ics battements 

 brusques et reiteres de leurs valves. MM. Quoy et Gaimard, qui firent 

 partie de I'expedition autour du nionde commandee par M. Duniont 

 d'Urville, racontent qu'ils furent oblige de courir apres des Limes pour 

 s'en emparer." — Chenu, Lef. Element. 101. 



* Lister, Exer. Anat. tert. auet. p. xlii. 



t Kirby regards the Pectens as, in some degree, the analogues of the 

 butterflies amongst insects, " and their flying, as it were, on the surface of 

 the water" increases the resemblance! — Bridgew. Treat, i. 254. This 

 seems to us a rich example of a false analogy. — Bosc aflirms that some of 

 the genus Venus can sail in the manner ascribed to the Pectens. — Hist, des 

 Coquil. iii. 41. And the Rev. Mr. Guilding discovered a genus allied to 

 Lima which swims " with as much ease as a fish," by opening and closing 

 the valves, and the action of the tentacular fringe of the cloak. — Mag. Nat. 

 Hist. ix. 194. 



§ Scottish Christian Herald, ii. 165 : " At the age wc saw it perform, 



