CRISTATELLA. 95 



vancing more and more towards perfection before our eyes, we can but 

 offer conjectures of the process whereby it is accomplished. 



Numerous ova, of various hue, according to their respective stages of 

 maturity, appear irregularly dispersed amidst the smooth and translucent 

 fleshy parts of the Cristatella — nor confined in any definite ovarium. — 

 Plate XXVIII. fig. 6. 



While retained within the zoophyte, perhaps each is invested by a 

 certain gelatinous matter, sometimes, but not invariably, present when 

 produced. Originally, or at an early period, the internal ovum appears of 

 dingy white, then greenish. Next, in maturity, it is a beautiful and singu- 

 lar object, of lenticular form, with dark brown sides, smooth and convex, 

 the edge environed by a vivid yellow circumferential margin, also begirt 

 by a row of spines, which terminate in as many recurving hooks. — 

 Figs. 7, 8, 9. The hooks are double, that is one recurves to either side of 

 the extremity of the spine. This portion seems of later formation. 



I cannot explain how the ova are produced by the zoophyte, whether 

 in the earlier part of the season they escape by some appropriate channel, 

 one or more, while the animal is fresh and vigorous. Neither do I know 

 that there is any precise reciprocal relation, collectively or individually, 

 between them and the hydrse. 



The principal mode of liberation is undoubtedly from the decay and 

 decomposition of the Cristatella, towards the close of autumn, for nothing 

 has proved its permanence to exceed a single season. Some survive 

 longer than others, as the extinction of life does not appear to be regu- 

 lated specially by abstract portions of time in any animated being : appa- 

 rently it is rather dependent on circumstances. 



Towards the end of autumn, all Cristatellss hasten to speedy decay. 

 The specimen, Plate XXVII. fig. 1, a very fine one, of unusual dimen- 

 sions, which was exhibited to the British Association, at Edinburgh, in 

 September 1834, had shrunk to half its original length within nine days 

 of its capture, many of the hydras having withdrawn from view. In 

 another week, not above a dozen, from 350 or more at first, composing 

 the luxuriant border, were displayed ; at which time the product had con- 

 tracted to a fourth of its pristine dimensions. All the hydrae ceased to 



