382 EVEXEXGS AT THE MICEOSCOPE. 



muricate appearance, and the tentacle terniinates in a 

 blunt point. The discal part of the bnlb is fringed 

 with a row of minute bead-like spherules. Around the 

 edge of the circumference of the disk, on the exterior, 

 are arranged eight beautiful and conspicuous auditory 

 vesicles. They are placed in pairs, each pair being ap- 

 proximate, and appropriated to each of the quadratures 

 of the circle. Each of these organs consists of a trans- 

 parent globe, not enveloped in the substance of the 

 disk, but so free as to appear barely in contact with 

 it : it contains a single otolithe, of high refractive 

 power, placed not in the centre, but towards the outer 

 side. The inexperienced naturalist, on first seeing 

 these organs, would unhesitatingly pronounce them 

 eyes, and the otolithe the crystalline lens. They are, 

 however, pretty certainly, rudimentary organs of hear- 

 ing ; the crystalline globule or otolithe being capable 

 of vibration within its vesicle. Their exact counter- 

 parts are found in many of the smaller Medusae, as we 

 lately saw in the Thaumantins. 



The disk is endowed with an energetic power of 

 contraction, by which the margin is diminished, ex- 

 actly like that of a Medusa swimming ; and the ten- 

 tacles have also the power of individual motion, though 

 in general this is languid, their rapid flapping being 

 the effect of the contraction and expansion of the disk, 

 producing a quick involution and evolution of the mar- 

 gin, and carrying the tentacles with it. Occasionally, 

 nowever, all the tentacles are strongly brought together 

 at tlieir tips, with a twitching grasping action, like 

 that of fingers, which is certainly independent of the 

 disk, and may be connected with the capture of the prey. 



Xow every detail of the structure here, as well a* 



