82 MARINE ANIMALS OF MASSACHUSETTS BAY. 



nate action gives to their movements a swinging, swaying charac- 

 ter, expressive of the utmost freedom and grace. Whether such 

 Fig. 116. ^ little community darts with a lightning-like speed 

 thi'ough the water, or floats quietly up and down, 

 for its movements are both rapid and gentle, it 

 always sways in this way from side to side. Its 

 beauty is increased by the spots of bright red 

 scattered along the length of the stock at the 

 base and tips of the Hydras, as well as upon the 

 tentacles. The movements and attitudes of the 

 tentacles are most various. Sometimes they 

 shoot them out in straight lines on either side, and then the 

 aspect of the whole thing reminds one of a tiny chandelier in 

 which the coral drops make the pendants, or they may be caught 

 up in a succession of loops or floating in long streamers ; indeed, 

 there is no end to the fantastic forms they assume, ever astonish- 

 ing you by some new combination of curves. The prevailing 

 hue of the whole community is rosy, with the exception of the 

 oil bubble or float, which looks a bright garnet color when seen 

 in certain lights. 



Let us now compare one of the Hydrae hanging from the stem 

 (Fig. 113) with the Hybocodon (Fig. 102). The reader will 

 remember the unsymmetrical bell of this singular Medusa, one 

 half of its disk more largely developed than the other, with the 

 proboscis hanging from the centre, and the cluster of tentacles 

 from one side. Let us now split the bell s<5 as to divide it in two 

 halves with the proboscis hanging between them ; next enlarge the 

 side where there are no tentacles, and give it a triangular out- 

 line ; then contract the opposite side so as to draw up the cluster 

 of tentacles to meet the base of the proboscis, and what have we ? 

 The proboscis now corresponds to the Hydra of our Nanomia, 

 with the cluster of tentacles attached to its upper edge (Fig. 

 113), while the enlarged half of the bell represents the shield. 

 If this homology be correct it shows that the Nanomia is not, as 

 some naturalists have supposed all the Siphonophores to be, a 

 single animal, its different parts being a mere collection of organs 

 endowed with special functions, as feeding, locomotion, repro- 



Fig. 116. Oil float of Nanomia ; greatly magnified. 



