THE MARGINAL CAPSULES. 87 



circle : tliey do not appear to be organically connected 

 wdth the tentacles. Each of these organs consists of 

 a transparent globe, not enveloped in the substance 

 of the disk, but so free, as to appear barely in contact 

 with it (see fig. 2) : it contains a smaller globule or 

 lens, of high refractive power, placed excentrically 

 towards the outer side.- The inexperienced naturalist 

 on first seeing these organs would unhesitatingly 

 pronounce them eyes. They are, however, considered 

 as rudimentarv oro^ans of hearino- • the crvstalline 

 globule or otolithe being capable of vibration within 

 its vesicle. Their exact counterparts are found in 

 most of the small Medusae., a tribe of animals, which 

 this tiny zoophytic embryo represents in its whole 

 form and structure. 



The disk is endowed with an energetic power of 

 contraction, by which the margin is diminished, 

 exactly like that of a Medusa in swimming ; and the 

 tentacles have also the power of individual motion, 

 though in general this is languid, their rapid flapping 

 being the eff"ect of the contraction and expansion of 

 the disk just mentioned, producing a quick involution 

 and evolution of the margin, and carrying the tentacles 

 with it. Occasionally, however, all the tentacles are 

 strongly brought together at their tips, as at fig. 5, with 

 a twitching grasping action, like that of fingers, which 

 is certainly independent of the disk, and may be con- 

 nected with the capture of prey. 



Several months afterwards, having obtained some 

 populous colonies of this species attached to al^a-, I 

 selected some, to examine afresh their embryology. 

 Some of the stalks were crowded with vesicles, which 



