OVUM. 



19 



In a certain number of the Campanulariae, 

 Sertulariae, and Tubulariae, of which the in- 

 ternal structure is more complex than in the 

 Coryne, and in which the Polype always na- 

 turally presents a branched form, or groups of 

 distinct Polype heads formed upon a common 

 stem by gemmation, it is now well ascertained 

 that the Polype state is not the only nor the 

 complete condition of the animal, but that by 



Fig. 13. 



Branch of Sertidaria geniculata, magnified, shewing 

 polypes, and ovigerous capsules. 



a process, in some instances similar to that 

 above described, in others, somewhat different 

 from it, a set of bodies, charged with the office 

 of the sexual production of the ova, are deve- 

 loped in place of the more ordinary Polype 

 heads or individuals. In the Campanularia ge- 

 latinosa, according to Van Beneden, the gene- 

 rative heads are close bell-shaped capsules, 

 within which small Medusoid bodies are deve- 

 loped by a process apparently analogous to 

 gemmation, or, at all events, without sexual 

 .generation, and each of these Medusoids be- 

 coming free, move about in the adjacent fluid 

 as independent animals. The farther destina- 

 tion or changes of these Medusoid bodies 

 have not yet been observed, but from parallel 

 observations in other similar animals, it is 

 believed that they afterwards attain to sexual 

 completeness, and form ova which are de- 

 veloped into the Polype form.* 



* See the View of Campanularia geniculata, by 

 Van Beneden, in Mem. de 1'Acad. de Bruxelles, 1844, 

 vol. xvii. ; and Ann. des Sc. Nat. torn. xx. p. 350, 

 1843. See also the very interesting account of Tu- 



But the interesting observations of Loven*, 

 and also some previous observations of Lis- 

 ter y, would show that in the Campanularia 



Fig. 14. 



Campanularia. ( From Desor.) 

 A, po rtion of a branched stem, magnified, c, 

 non- sexual head or individual ; gg, two capsules, or 

 modified heads, producing Medusoids by gemma- 

 tion, in different stages ; m, Medusoid escaping ; 

 m' m", Medusoids more advanced, moving freely by 

 the contractions of their disc. 



geniculata, and in Tubularia, the Medusa-like 

 bodies may in some instances not be detached 

 from the Polype heads or capsules, and may 

 even not be developed fully into the Medusa 

 form, but nevertheless produce their ova in 

 that attached situation, and thus give rise to 

 ciliated embryoes, which, when excluded, move 

 for a time, and then, like the others arising 

 from the detached Medusa?, become converted 

 into Polypes. 



According to Desor, of Boston J, the same 

 Campanularia may at one time produce two 

 kinds of capsules, the one set containing ova 

 the other spermatozoa ; the Medusoid progeny 

 not being developed, and the ova giving rise 

 to forms similar to the parent Polype : and 

 M- S. Schultze, of Greifswald, has confirmed 

 this statement, apparently without the know- 



bularia, in Dalyell's Remarkable Animals of Scot- 

 land. 



* In Wiegmann's Archiv, 1837. 



f Phil. Trans. 1834. 



t Ann. des Sc. Nat. 1849, xii. p. 208. 



Muller's Archiv, 1850, p. 53. 



c 2 



