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PROCEEDINGS OF THE 



[Dec, 1856. 



they reach the origin of the chymiferous tubes, and so whether the 

 streams for the larva's nourishment are not sometimes drawn even 

 from the circulating fluid itself of the parent. — Another question, 

 which would also have been immediately set at rest by such an 

 observation, is that as to the nature of the imbibing process. For 

 myself, however, I can have no doubt from the following consider- 

 ations, that it is m no respect other than a simple ciliary phenome- 

 non. In the first place the act of suction, properly speaking, ne- 

 cessarily implies a cavity exhausted by the action, of muscular 

 or at least contractile tissues, whereas as before stated, the probos- 

 cidian tube and whole body of the larva in this instance is never so 

 still and moveless as when engaged in the process of imbibition. 

 On the other hand I have observed strong ciliary action over the 

 oral bulb of the larva, when moving free in the bell-concave, which 

 is amply sufficient to account for the whole phenomenon of imbibi- 

 tion. If, for example, we suppose the proboscis to be plunged into 

 the stomach when full, of fluid chyme into which its oral extremity 

 would thus be dipped, ciliary currents round the oral bulb could 

 be so co-ordinated as to centre in the mouth as a- vortex, where the 

 fluid so introduced would be immediately taken up by the ciliary 

 action within the scyphon and driven on in a current towards the 

 stomach, and it is this current which is visible through the trans- 

 parent tissues of the larva when feeding. 



Up to this point in the growth of the larva we observe no differ- 

 ence between it and other hydroids saving only its manner of feed- 

 ing, to which no parallel, that I am aware of, has yet been noticed. 

 If my reasoning be correct, it deposites itself in the bell-concave of 

 the parent medusa, perhaps as a spherical planula, assumes an 

 elongated proboscidian; form, developes first two tentacula, then 

 four, by which it moves or locates itself, or when, located maintains 

 its hold. Up to this stage, then, it is the exact analogue of what 

 takes place in Tubularia up to the time of the escape of the young 

 hydroid, from what has been called its ovarian capsule, but which, 

 in the species of our own: coast, at least, is a genuine proboscidian 

 Medusa, differing in no essential respect from other Medusae, unless 

 we make an artificial distinction of the circumstance, that it lives 

 and produces its young without becoming free. If the Medusa of 

 Tubularia is only an ovarian capsule, then our free swimming 

 instinct-gifted Turritopsis is an ovarian capsule also. In both 

 there are distinct sexual organs surrounding a proboscis containing 

 the digestive cavity — in both there is a swim-bell containing a 



