ALCYONELLA. 105 



They are sometimes seen while the hydra is active, vigorous, and 

 symmetrical, fig. 7. When escaping towards the end of June, I could not 

 refer them to any but perfect specimens, — nevertheless, a great modifica- 

 tion ensues as autumn advances near to its termination. The body of the 

 hydra within the integumenta^ covering, wastes away, and the integu- 

 ment itself enlarges proportionally to receive the ova from below, where 

 they are in all appearance generated. At this juncture they rise upwards 

 into it, as into a vascular receptacle. Here they become at length evi- 

 dently suspended, and tossed about amidst the fluid contents of the now 

 turgid integument. Ligaments, as in other ascidian hydrse, probably secure 

 the body of the animal originally, but as these changes succeed, its extre- 

 mity seems to be free ; and as the turgidity augments, the body is ob- 

 served completely attenuated among the ova. 



When several ova are together within this integument, as I design it, 

 their motion is neither rotatory nor progressive, but rather a confused 

 tumbling over each other. This movement continues where the hydra has 

 totally decayed, and only the hollow prominence covering the included 

 ova remains. But the ovum itself is entirely devoid of spontaneous mo- 

 tion ; it has no such faculty, corresponding in this respect with that of the 

 Cristatella ; and differing entirely from the nature of the active ciliated 

 gemmule of the Actinia and the Flustra. It resembles a real ovum with 

 a hard shell, or it may be membranaceous, for, in such minute bodies, it is 

 difficult to determine the quality and proportion of resistance on pres- 

 sure. 



For the purpose of ascertaining whether the motions which I beheld 

 were voluntary or accidental, I selected a hydra advancing to decay, with 

 four ova in the vascular distension. Two were in irregular motion, some- 

 times tumbling over, and a third was moving also. But on slitting the in- 

 tegument with small sharp-pointed scissors, whereby all four were liberated, 

 they remained perfectly quiescent and stationary, floating like others on 

 the surface of the water. 



The motion of the ova being therefore involuntary while confined with- 

 in the hydra, it must ensue from some external influence, — and probably 

 from an invisible absorption and discharge of -water by the product. But 



VOL. II. o 



