THE LOWER FORMS OF LIFE. 99 



organisms appear like Medusae turned upside down, being generally 

 about an inch in height. Their attachment by the hydrorhiza (a) 

 is not permanent. As shown in the figure, the tentacles (5) are 

 eight, sometimes nine in number, and appear like tufts of flowers 

 round the rim of a glass vessel. 



The granular matter of which these organs of prehension are 

 composed passes between membranous folds and terminates in a rim 

 surrounding the mouth of the polypite (a). In another genus, 

 Carduelia, these tentacles form a complete rim round the edge of 

 the cup. They have generally sucker-like appendages at their 

 extremities ; but in others they are club-shaped, like those in the 

 Zoophyte, Coryne. 



The Lucernaria are of a pink colour, and can close in their cup 

 by the contraction of a series of muscular fibres which pass round 

 its rim and radiate towards the polypite (a, Fig. 123). By the 

 alternate opening and shutting movement thus produced, they some- 

 times swim through the water, with their cup everted, in a respectable 

 Medusa-like fashion. Most of the writers since Johnston's day have 

 copied his figure of Lucernaria auricula. It is only fair, therefore, 

 to give his other figure, L. campanulata, a like chance of popularity, 

 which I have accordingly done. 



CHAPTEE V. 



REPRODUCTION OF THE HYDROZOA. 



THE Phosphorescence of the Sea is a subject of sufficient interest 

 and importance to merit a short space before we close the history of 

 the Hydrozoa. 



Almost all the Medusae and Physalia and some of the corallines 

 among the Hydrozoa are phosphorescent, and no one can have 

 witnessed this phenomenon, even as seen on our own shores, without 

 being struck with its singular and weirdlike beauty. In other 

 countries it is even more striking. 



Mr. Bonnycastle thus describes a scene of this kind which he saw 

 on the 7th of September, 1826, in the Gulf of St. Lawrence : 



" While it was very dark a brilliant light, like that of the aurora, 

 was seen to shoot suddenly from the sea in a particular quarter. It 

 spread thence over the whole surface of the water between the two 

 shores of the gulf, and shortly there was presented one blazing sheet 

 of awful and most brilliant light, in which many large fishes were 



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