^'^^ 65, 66. 



THE ACALEPHAE. 



69 



CHAPTER VIII. 



ORGANS OF SECRETION. 



§ 65. 



The air-eavity of certain Siphonophora, which is surrounded by a dou- 

 ble membrane, ought probably to be regarded as an organ of secretion; for, 

 according to many naturalists, the air contained could not have been de- 

 rived from without, and consequently was secreted by the sides of the 

 internal membrane. ^'^ 



CHAPTER IX. 



ORGANS OF GENERATION. 



§66. 



Reproduction by Jissuration and gemmatmi with the Acalephae has 

 been observed only in the youngest states of certain Medusae.''^ But repro- 



cavity, belongs probably to the aquiferous system. 

 That which in Porpita has been talien for a mouth, 

 belongs probably, also, to the same system. I 

 would not, however, deny that another significa- 

 tion may be given to the so-called resph-atory and 

 digestive organs of the Siphonophora. 



If one prefers, with Philippi, to regard the open- 

 ing between the tentacles of Physophora, Velella 

 and Porpita, as a mouth, then the cavity of these 

 tentacles should belong to the aquiferous system. 

 Moreover, these tentacles, as to then* form and mo- 

 bility, remind one of the pedicles of the Echino- 

 derms ; but it is remarkable that they can absorb 

 food. 



Sars (Faun, littoral. Norveg. p. 34, 42, Tab. VI. 

 fig. 3, gg. and Tab. VII. fig. 3, e.) has observed in 

 the interior of the cartilaginous, natatory pieces of 

 the Physophoridae and Diphyidae, aquiferous 

 canals which are probably of a respiratory nature. 



Hollard, likewise, regards the hollow and tubuli- 

 form tentacles of Velella as aquiferous tubes, and 

 in this way, as the tentacular feet of the Echino- 

 derms, includes them in the aquiferous system. See 

 Ann. d. Sc. Nat. III. 1845, p. 250. 



1 Many naturalists entirely deny the presence of 

 openings in these agrial cavities, and do not admit 

 that they are filled with gas. Thus Philippi 

 (Muller's Arch. 1843, p. 63) affirms to have found 

 neither external opening nor air in the pouch at 

 the end of the longitudinal canal of Physophora 

 tetrasticha. Olfcrs (Abhandl. d. Berl. Akad. 

 1831, p. 165) has not been able to find in Physaiia 

 the opening of the internal sac, said to be near the 

 one of the external sac. In fact, Bennett (Proc. 

 Zool. Soc. London, 1837, p. 43 ; and fViegmann''s 

 Arch. 1S3S, II. p. 332), with the same species, 



has not seen an opening of this cavity, and was 

 unable to force an- from it. Future researches 

 must determine if these pouches have not a respir- 

 atory function. 



1 See, upon this subject, the Embryology of these 

 animals, beloy. It is not yet demonstrated that 

 adult Acalephae reproduce by fissuration ; and 

 although Mertens (M6m. d. I'Acad. de St. Peters- 

 burg, II. p. 494, PI. I. fig. 2-4, and p. 521) has 

 observed detached corpuscles from the body of 

 Cestum and Cydippe swim freely about, and rap- 

 idly enlarge, yet his observations are here lim- 

 ited. 



In the same way. Will (Horie tcrgest. p. 42) has 

 seen analogous bodies detached from Eucharis, 

 and has found in the water others supposed to be- 

 long to the Ctenophora, but has not traced their 

 further condition. 



Propagation by buds has also been found with 

 the Acalephs, through the excellent researches of 

 Sam (Fauna httoral. Norveg. p. 11, Tab. IV. fig. 

 8-12), for this observer has seen on the external 

 surface of the tubuUform stomach of Cytaeis octo- 

 punctata, and upon the four ovaries of Thauman- 

 tiasmullicerrata, small campanuliform Acalephs 

 resembling their parent, in the process of develop- 

 ment, and which were finally detached. In the 

 genus Agalmopsis which is aUied to Agalma, 

 Sars has observed (Ibid. p. 38, Tab. VI. fig. 14-17) 

 campanuliform bodies sprout out between the pre- 

 hensile filaments and the tubuliform stomach, and 

 which were finally detached, swimming freely like 

 the Disoophora. According to Sars, also (Ibid, 

 p. 43, Tab. VII. fig. 11, b. 13, b. and 14), there is, 

 likewise, an analogous mode of propagation with 

 Diphyes.* 



* [ § 66, note 1.] See also Huxley (Ann. Nat. they multiply by germnation as well as by ova. 

 Hist. VI. p. 394), who has described the reproduc- See, also, Muller's Ai'Ch. 1S51, p. 3S0, Taf. XVII. 

 tlve processes of the Diphyidae, and shown that^ — Ed. 



