182 ZOOPHYTES. 



Whether white or yellow, they are distributed throughout the whole 

 interior of the vessels, precisely in such places as might be easily acces- 

 sible by the planulse. They are often seen in greater profusion on the 

 sides, just at the surface of the water ; and they are generally found 

 higher and higher in proportion as the vessel is successively replenished. 

 If some be seen adhering close to the edge of the water, let the vessel 

 be still more replenished, others will subsequently adhere above them, 

 should propagation continue advancing. Meantime, the observer may dis- 

 cover white or yellow corpuscula floating at the surface, which he would 

 conclude to be spherules ; but careful inspection proves them inverted 

 nascent Sertularise, whose root has failed of adhesion. 



In all this, it is impossible to avoid admitting the strict analogy be- 

 tween the preceding stages and circumstances of the progeny of the Me- 

 dusae, and those distinguishing the early existence of the Sertularise. 



Following the design of Nature, it may be presumed that a regular 

 tendency to adhere, as the planula becomes motionless, is for securing the 

 diffusion of the root, as a sufficient foundation for the rising product. 



Shortly after a glass cylinder had received prolific specimens, nearly 

 a circle of spots appeared on the sides. The cylinder being emptied and 

 replenished with water, an inch and a half higher than the circle, eight or 

 ten spots, also higher, appeared subsequently. Twenty or more of the 

 lower circle had become affixed in such a manner that their stems issued 

 downwards ; while the stems of the rest, adhering flat to the side of the 

 vessel, shot forth horizontally. Spite of that irregularity, some of the in- 

 verted nascent products acquired five cells ; and hydrse flourished from three 

 of them. The young at the bottom were numerous ; those on the sides 

 few. All the vesicles consigned to the vessel were white ; all the planula" 

 quitting them white ; and all the spots were white likewise. 



Adult specimens, with yellow vesicles, having been consigned to a 

 more capacious vessel, yellow spots were soon after observed on the side, 

 Just at the edge of the water, or rather above it. Another smaller vessel 

 being now sunk inside, to raise the water still higher, many additional 

 spots appeared, within 24 hours, on that part of the side, which the ele- 

 vated water reaching, had covered. Numerous yellow planulse were like- 



