MEDUSA BIFIDA. 113 



bottom of the cleft, is surmounted by a black speck, which a powerful 

 magnifier exposes as a number of smaller specks on a lighter ground. This 

 somewhat resembles the structure of the specks terminating the rays of 

 the star-fish. Many consider the specks which are disposed at intervals 

 on the margin of large and of smaller Medusae as ocular, but it might be 

 well to investigate whether, both there and in the Asterise, they are not 

 rather of a glandular nature. — PI. XVIII. fig. 6, magnified lobe and cen- 

 tral cone. The whole surface of this minute Medusa is finely speckled or 

 granulated, which, as the other parts, can be clearly discovered only by 

 microscopic powers. — PI. XVIII. figs. 7, 8. 



The animal moves by jerks or bounds, from collapse of the body and 

 percussion of the water by the lobes. As all other Medusae, it shews a con- 

 stant tendency to seek the surface by an oblique or perpendicular ascent. 

 Sometimes, but rarely, in reversing itself, the proboscis appears like a 

 crest above, fig. 3, which affords the most favourable view of the whole 

 formation ; and it generally drops gently down among the water, with the 

 proboscis below and the arms extended. Resting in equilibrio, the pro- 

 boscis is downwards, and the lobular arms slightly recurved, fig. 2. 



This Medusa courts a moderate degree of light. Then it always rises 

 to the surface, an invariable characteristic of the Medusarian race, for it 

 seems adverse to their nature while in vigour to remain below. Weak- 

 ness and inaction are denoted by their permanence there. But the light 

 beinf bright the Medusae incline to shun its intensity ; though heat and 

 licht be the chief incentives to motion, not only among them, but of many 

 of the lower tribes. 



For the most part, the existence of the cloven Medusa is very tran- 

 sient. It appears unexpectedly, and in a few days it decays or vanishes. 

 With the utmost precautions, I have never been able to protract its 

 life above 55 or 60 days from its origin. On its earliest escape to an 

 independent existence, it seems fully developed and endowed with 

 ample vigour. No sensible increment, accession, division, or reduction 

 of any portion ensues during the whole currency of the period here 

 specified, nor any change or alteration farther than that concomitant 

 on declining strength and activity. The size of the specimens repre- 

 VOL. I. ^ 



