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PROCEEDINGS OF THE 



[April, 1857. 



ginal capsules, which latter also are all at equal distances from 

 each other. Coloration is confined to the digestive cavity, the 

 sexual organs, and the tentacular bulbs. In a limited number of 

 genera, ocelli are present according to observers of the most un- 

 doubted authority. They occur near the marginal cord on the 

 bulbs of tentacula, and according to Professor Agassiz, on the 

 upper part of the representatives of the marginal capsules in his 

 genus Tiaropsis. 



The larvae are Campanularidas, branching or creeping horny 

 polypidomata of great delicacy; each polyp being housed in a rather 

 deep, more or less conical or hemispherical horny cup. This 

 cup, unlike the same part in the next group is mounted on an 

 usually annulate foot-stalk or branchlet. Near the axils of 

 these branchlets is the general position of the medusa-bearing 

 polyps, whose cups are usually much deeper than those of the 

 digestive polyps. The digestive polyps are distinguished 

 from those of the next group by having the mouth at the extremity 

 of a proboscidi-form process from the area within the circle of 

 tentacula. The prolific individuals are said to be at first tentacu- 

 lated polyps like the digestive ones, but they afterwards, dwindling, 

 lose their tentacula, retaining only the mass of the body in which 

 a trace (sometimes very distinct) of the digestive cavity may be 

 seen, and which remains as a stopper over the mouth of the cup. 

 On the slender outstretched pedicle of the polyp and in the cavity 

 of the cup, the medusae are developed, according to the Exostome 

 method : frequently however remaining mere pedunculated cysts 

 which nurse planules. As the medusa buds increase in size the 

 polyp-head usually diminishes and at last dwindles so as to leave 

 only a slight trace of its existence. Between it and the lid of the 

 cup the liberated medusa, escape one by one, forcing themselves 

 through by violent exertions. From their manner of growth their 

 appearance before liberation is, except in deep-belled species, 

 much more like that of the digestive polyps than is the case 

 among Endostomata. 



There are at least two under-groups in this division which are 

 distinguished by the presence or absence of ocelli. The genus 

 Obelia, (ex. Thaumautias plana Sars.) may perhaps constitute 

 a third under-group on account of its depressed form, its stiff 

 short numerous tentacula, and their connection with its marginal 

 capsules. 



