416 Mr. S. P. Woodward un the Habits of Bivalve Shell-fish. 



happens if the water is artificially coloured with indigo; the 

 time required depending partly on the quality of the pigment, 

 which is sometimes so fine as to pass through the living filter. 

 When one Pholas was disturbed by another, or incommoded by 

 particles too large for its siphon, it closed its valves and partly 

 retracted the siphons, making a small jet of water. If taken 

 from the pan suddenly, the siphonal orifices closed spasmodically, 

 so that no water could escape, and the siphons could not be with- 

 drawn ; after a moment the orifices relaxed, and the water w-as 

 spirted out. The tentacular cirri are extremely sensitive, and 

 contract directly they are touched, but the mantle may be di- 

 vided with fine-pointed scissors, so as to show the gills, without 

 causing any alarm to the animal, after the sphincter surrounding 

 the foot has once been divided. It was my wish to preserve ex- 

 amples of each species with the siphons protruded, and to this 

 end I allowed some to remain in stale water, thinking they would 

 lose the power of retraction, or die extended ; day after day the 

 siphons became longer, until they were twice their proper length, 

 the currents ceased, and at last the valves fell off by the decom- 

 position of the mantle; but when I attempted to remove the 

 animal, the siphons slowly contracted until completely with- 

 drawn. 



Another small vivarium contained a few shells from five fa- 

 thoms water ; including the young of the edible mussel an inch 

 in length, Syndosmya alba, Nucula nucleus. Some others were 

 tenanted wath the common cockle, Donax anatinus and Tellina so- 

 lidula and tenuis, obtained from the sandy shore at Denge Ness, 

 where the sea goes out nearly half a mile, leaving a wide waste of 

 ripple-marked sands without any trace of life, save the castings 

 of the Annelides and an occasional dimple made by a cockle or a 

 Donax. But of life there was plenty, as we might be sure from the 

 flocks of gulls which retreated before us; and on exploring with our 

 hands we found the whole beach planted with Tellens, in a vertical 

 position, as thickly together as holes made simultaneously with 

 the fingers. Lower down there must have been many other shell- 

 fish ; for the high-water line was strewn with Mactras and Car- 

 dium echinatum, Solen marginatus and ensis, spawn of Natica and 

 whelk, &c. The common cockle is an excellent subject for obser- 

 vation on account of its activity, the beauty of its fringed siphons, 

 and the whirlpools it creates in the water. Donax has short 

 siphons, with foliaceous cirri ; Tellina and Syndosmya have very 

 long siphons, sometimes four or five times as long as the sliell, 

 very slender and transparent, with simple orifices. Those Tel- 

 lens and Donaxes which were allowed sea-sand soon buried 

 themselves, protruding only their siphons. In a short time the 

 sand in which they were buried became so firm that it required 



