CORYMORPHA NUTANS. 211 



circular canal. Of these bulbs one is much larger than any of the others, and is continued into 

 a tentacle, while none of the others present any trace of such an appendage. They all contain 

 brownish-red pigment-granules, but no true ocellus can be recognised. There is a broad velum. 



The solitary tentacle is largely developed, and consists of a very extensile moniliform cord, 

 presenting, when extended, the appearance of ten or twelve little spherules distributed at equal 

 distances upon a cylindrical string. The last of these spherules exactly terminates the string, 

 and is larger than the others, while one or two situated near the proximal end are smaller and less 

 distinct. The spherules are composed of accunuilations of thread-cells, and the connecting cord 

 has its axis occupied by an rminterrupted tube directly prolonged from the cavity of the bulb at its 

 root. During contraction the spherules assume the form of circular discs (fig. 4), and in extreme 

 contraction the connecting cord disappears and the surfaces of the discs are brought into contact. 



The manubrium is large and sub-cylindrical, and the mouth is without tentacula or lobes. 



From the above description it will be at once apparent that the medusa of Corymorpka 

 nutans belongs to a form to which Edward Forbes has given the generic name of Steemtrupia} 

 Of this relation between Steemtrujpia and Corymorpka Forbes himself had a suspicion ; indeed, 

 he expresses a belief that his Steenstriqjia rubra will turn out to be the free medusa of 

 Corymorpka nutans. The development of the medusa from its first appearance to its liberation 

 has been already traced (see above, p. 77). 



The medusae when they become free are about 53 inch in diameter (fig. 3), and as yet show 

 no trace of generative elements, and though I kept them alive for more than a week they 

 scarcely increased in size, and never presented any indication of ova or spermatozoa. 



I oljtained, however, by means of the towing-net, in the neighbourhood of the locality which 

 produced the Coryinorpha, a little medu.sa (figs. 5, 5") regarding which there can be no doubt that 

 it is a more advanced stage of the gonophore of Corymorpha nutans. It was about four times 

 the size of the newly liberated medusa ; the tentacle had proportionately increased in length and 

 now presented upwards of forty spherules, while the radiating canals at their origin from the 

 manubrium curved upwards towards the summit more decidedly than in the younger form. 

 The generative elements— not yet, however, fully developed, and apparently male, though from 

 their immature condition no active spermatozoa could be detected — were very distinctly visible 

 as a pale yellow mass between the endoderm and ectoderm of the manubrium, which was rendered 

 tumid by their presence (fig. 5). In all other respects the little medusa was identical with the 

 younger ones, and continued to present the acuminated summit, which was even still traversed by 

 the canal which originally maintained a communication between the tube of the supporting stalk 

 and the cavity of the manubrium. 



It would thus seem that the changes undergone by the medusa between the time of its 

 liberation from the trophosome and its attainment of sexual maturity are of little importance. 

 It is worthy of especial attention that there is never more than a single marginal tentacle developed. 



Free Frustules. — But besides the production of medusiform sexual buds, I have also witnessed 

 in Corymorpha nutans another process of reproduction, very remarkable, but of whose exact sig- 

 nificance I was unable at the time to speak with as much confidence as I can now do. In a glass 

 jar containing living specimens of Corymorpha, which had been in my possession for more than a 

 fortnight, I observed attached here and there to the surface of the glass minute oblong bodies 



^ Forbes, ' British Naked-eyed Medusae,' p. 72. 



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