ALCYONIUM. 49 



displayed from three such spots, and favourable observations on the day 

 following, shewed their complement of tentacula as amounting to about 16. 

 A row of stout cilia, rather towards the exterior of each tentaculum, and 

 somewhat darker, maintained a regular rapid action, inclining upwards by 

 ascent along it, and downwards by descent on the other side. Thus the 

 whole border of cilia kept up a perpetual current. 



The hydra protrudes laterally or obliquely from the side of the ori- 

 ginal cell, not vertically from the surface. — Figs. 16, 17. 



As in some other species, the internal organization, the intestine 

 forking upwards from below, together with what I concluded the dark 

 contents of the stomach, agitated by a kind of revolution, were exposed 

 by the transparence of the body. 



Besides these nascent animals, then mature, and displayed from their 

 cells, each of many spots shewed an immature hydra, with the tentacula 

 in a contracted state. 



The period required for bringing the nascent hydra to maturity equal- 

 led nine, ten, eleven, or twelve days, computing from the escape of the 

 gemmule. Here the original spot following the stationary gemmule dif- 

 fuses into compartments ; or, to speak more correctly, these are generated 

 or evolved from its existence. Had their preservation long enough been 

 practicable, doubtless a hydra would have sprung from each. Three com- 

 partments were thus generated from some, but only a single hydra, the 

 first, came to maturity. 



No peculiarity of the surface distinguished the specimen, Plate XVI. 

 fig. 1. But the enlargements were hollow. Having been twelve weeks 

 in my possession, and hydrae ceasing to protrude, I cut several slices off 

 different parts in the middle of winter. Numerous minute white corpus- 

 cula, of singular appearance and motions, were speedily discharged from 

 them. All were of the most irregular shape, somewhat flattened ; 

 the largest portion begirt by a row of short cilia ; one had a tendency to a 

 circular form, another to elliptical, and a third seemed compounded of two 

 in union. Interanea and a dark solid substance like an ovum were indis- 

 tinctly seen through the integuments of several. They were active and 

 vigorous, performing short excursions, or tumbling over in the water. 



VOL. II. G 



