416 Y. \V. GAMBLE AND FUKDEIUCK KEEBliE. 



fertile patches arrive at maturity simultaneously, and con- 

 sequently the egg-capsules occur in great numbers at the 

 approach of the highest spring tides. These egg-capsules 

 may be collected on the beach by first tapping the sand and 

 driving the Convoluta below the surface, scooping up a 

 little sand, shaking it with water in a test-tube, and catching 

 the slowly sinking white capsules with a pipette. 



The general features of the development of Convoluta 

 have been described by Georgevitch, but the remarkable 

 phenomena that accompany oviposition have not been pre- 

 viously recorded. The eggs are, or at least may be, fertilised, 

 and the egg-membrane formed within the body of the parent. 

 The discharge of these eggs takes place in one of two ways. 

 In the less general method the eggs are laid singly, and no 

 rupture of the parent takes place. The more general method 

 consists in the discharge of a number (5 to 13), and the 

 formation around them of a mucilaginous capsule. This 

 capsule appears to be secreted by the skin of the parent. 

 In its formation, the body of the animal often undergoes 

 violent changes. Rupture of the tissues, and indeed a complete 

 break across the middle of the animal, usually follow. The 

 spent anterior end crawls away, responsive, like the intact 

 animal, to the directive stimuli of light and gravity. The 

 tail end, devoid of tropisms, ejects the spermatozoa, remains 

 for a time attached to, or in the neighbourhood of, the egg- 

 capsule. It may swim ceaselessly in devious spirals, then 

 come to rest, and after a day or two disintegrate. 



The surface of the capsule is sticky at the time of laying, 

 and adheres to sand particles, thus being anchored. It is 

 covered more or less closely with the disjecta of the parent, 

 which afford a nidus for the development of many other 

 organisms (PI. 30, fig. 3). The eggs are laid as well in 

 darkness as in light. The embryos usually hatch in from 

 five to seven days, though the incubation period is very 

 variable. Before hatching, the embryos may be seen revolving 

 vigorously within the membranes, and occasionally, owing to 

 exceptional thickness of the membrane, tlie rotating stage is 



