Chap. VIII. 



CLYTIA CYLINDRICA. 



307 



Fig. 41. 



Free medusa of Clytia ct- 

 LiNDRiCA with eight eyes and 

 eight tentacles, and as many more 

 rudimentary ones. 



Figs. 43 and 44. 



there is a hollow, globular, ocular vesicle (PI. XXVII. Figs. 8 and 9, /), which 

 stands out from the disk, and is attached by one side. Each of these eight 

 vesicles contains a single, highly refractive, spherical body. Across the lower side 

 of the disk there is a septum or veil, which has an opening (a) in its centre 

 equal to about one half the breadth of the whole. The four rudimentary tenta- 

 cles, which are at first mere swellings, soon become conical, 

 their tip lengthening moi-e and more, till we have four short 

 tentacles, similar in all other respects to the first four tenta- 

 cles seen at the base of the chymiferous tubes when the 

 Medusa escapes from the calycle. Soon after the rudiments 

 of eight additional tentacles (wood-cut 41) appear, which, 

 as the Medusae grow older, are probably further developed. 

 The ovaries increase slightly in size, hanging like pouches 

 from the chymiferous tubes. The chymiferous cavity shortens as the lobes of the 

 actinostome are more deeply cleft. The opening of the veil grows larger and 

 larger, and the spherosome more depressed, with increasing size. 



Proles hydroidea. — The sterile hydra3 have sixteen tentacles ; the stems of the 

 single individuals are either connected by a creeping base, or ramify two or three 



times. The bell is deep, and has ten teeth 



along its edge ; it equals in length half the 



length of the stem (wood-cut 42), which is 



straight, rather stout, with three or four 



rings near its base, and two at the base 



of the bell. In the only specimen in which 



reproductive calycles were found, they were 



placed at the base of a branch ; they are 



smooth, increasing in breadth (wood-cut 43) 



from the base, with a slight constriction 



near the extremity ; when seen edgewise 



(wood-cut 44), they are very much flattened, 



and uniform in breadth. There are three 



rings at the point of attachment of the fertile calycle, the flat side 



of which is turned towards the main stem. The calycles contained 

 only five medusae-buds. 



Conclusions. — The Campanularians, thus far described, have all been referred to 

 the genus Clytia Lamx., in order to remind the reader of their systematic position, 

 according to the present state of our knowledge of the Hydroids. A comparison 

 of the preceding descriptions cannot fail, however, to show that we have here three 

 different generic types, two of which produce medusa? differing as widely in their 



Reproductive calycle of Clytia 

 CYLINDRICA, Seen, Fig. 43, from the 

 flattened, and Fig. 44 from the nar- 

 row side. 



Sterile hydra of 

 Clytia cylin- 



