204 



NANOMIA CARA. 



the different phases In which the chymiferous tubes are mere pouches 

 (a, Fig. 337), then large tubes connected by a circular tube {b, Fig. 337), 

 till finally the bell becomes somewhat expanded at one pole, and the 

 tubes have a tendency to bend, as in c, Fig. 337, when the difference 

 between the two kinds of chymiferous tubes is quite marked, although 

 the mode of attachment of the Medusa and the shape of the bell remind 

 us strongly of Tubularian Medusae buds, and we find no trace as yet of 

 the wing-shaped appendages, and of the difierence of outline of older 

 Medusae, when seen from different sides. 



As there is a portion of the axis, immediately beneath the float, 

 which is free from swimming-bells, we find also under the swimming- 

 bells a small part of the axis bare ; we soon, however, come upon a 

 cluster of small buds entirely different in character from those found 

 Fig. 338. under the float ; these are polyps, or feeding- 



mouths, in different stages of development. The 

 polyps (Medusae) to which this set of buds give 

 rise are of very different characters ; they are of 

 three kinds, and nearly equally distributed along 

 the remamder of the axis, no part of the axis 

 being reserved for any special kind of polyps ; 

 the most prominent kind, and the largest, are 

 the Hydra-mouths (Fig. 338), which are the most 

 active, and in which we find, at the point of junc- 

 tion with the axis, a cluster of long tentacles, along 

 the thread of which are fastened, by a short han- 

 dle, a knob-like appendage ; these are the tenta- 

 cles which are so prominent, and assume such 

 manifold attitudes when the community is at rest 

 or in motion. The polyps are open at the distal extremity, the open- 

 ing being frequently expanded like the disk of a leech, or simply flaring 

 trumpel>shaped ; they are exceedingly contractile, and sometimes ex- 

 pand far beyond the axis in search of food ; they communicate by 

 means of a somewhat narrow neck with the main axis, so that the food 

 which is taken in by any one of these mouths helps to feed the whole 

 community, and circulates freely in the main axis, and in every polyp 

 and swimming-bell. The clusters of tentacles are protected by a shield- 

 like scale (Deckstiick), to the nature of which I shall refer hereafter ; 

 this scale is triangular, with rounded extremities, and through the mid- 

 dle of it passes a thin tube, which connects with the main axis, making 

 a kind of knee immediately above the point of junction ; the upper 

 shield of Fig. 338 shows plainly the mode of connection. The knobs of 



Fig. 338. Cluster of MedusEe (feeding polyps) of the fii-st kind formed, in the younger stages, 

 with tentacular knob and scale. In the upper part of the figure a closed bud, with an oil-bubble, 

 is seen ; this bud is ready to be liberated and become an embryonic community, like Fig. 346. 



