80 CRISTATELLA MUCEDO. 



spring from both faces of the disc, just -within the annulus, and thence radiate outwards, 

 extending for some distance beyond the margin. The spines springing from the more convex 

 face are somewhat longer and more numerous than the others, and ahemate with them. All 

 the spines are terminated by two, three, or four curved hooks resembling grappling-irons. 

 Towards the end of summer, the statoblasts occur in considerable numbers in the interior of 

 full-grown specimens, and are visible through the transparent tissues of the animal. On the 

 death and decay of the coencecium they are liberated, when they become attached, by means of 

 their hooked spines, to various aquatic plants, and ultimately open for the escape of the young, 

 by the separation of the two faces, at the commencement of the following summer. The young, 

 on its escape from the statoblast, is at first solitary, but is rapidly multiplied by the pro- 

 duction of gemmse. 



I have never met with Cristatella later than the autumn ; it seems to be strictly annual in 

 its duration. 



