126 THE AQUARIAN NATURALIST. 



Those that were prolific extended about a line in 

 length, and were filled with yellow, globular corpus- 

 cles, about twenty-four in each (PL II. fig. 6, b, d). 



About fifty PlanulcB issued from the different vesi- 

 cles on the 8th of July. These were about a third of 

 a line in length ; the body plump, nearly round, but 

 somewhat flattened below; of a smooth, uniform 

 aspect, and darker in colour than straw-yellow. In 

 the course of their escape they were evidently sus- 

 pended from various parts of the specimen by an 

 invisible thread; but, on reaching any solid surface, 

 they advanced with an equal gliding motion, re- 

 sembling Planarice (PL II. fig. 6, c) . 



Many Planula continued quitting the vesicles from 

 the 8th to the 12th of July. They spread on the 

 bottom, and crowded together on the sides of their 

 vessels. Numerous dark green, thick, obtuse spines 

 were observed rising from spots on the bottom of the 

 glasses (PL II. fig. 6, g) ; and, on the 14th of the 

 month, several of these had evidently enlarged as 

 buds (PL II. fig. 6, /), which, next day, and on the 

 day following, had in many instances become deve- 

 loped into Hydrse (PL II. fig. 6, g). The spine is at 

 first dark green, thick and obtuse ; when further ad- 

 vanced, the summit enlarging exhibits the Hydra as 

 a green bud within its cell, the "spine" becoming 

 the sustaining stalk. Also the green colour of the 

 stem demonstrates the existence of a central pith. 



Illustrations of the process of progressive growth 

 may likewise be witnessed in this Sertularia in its 

 earliest stages. An enlargement appears at the summit 

 of a stalk, which is found to be invested by a deli- 



