56 



THE POLYPI. 



<^§ 51, 52. 



§51. 



III. There are Polyp-colonies wliich contain two kinds of individuals, 

 those which are sexless, and those having sexual organs only at certain 

 epochs. These last are campanulate or medusoid, and their sexual organs 

 are developed in various parts of their body. 



In Coryne ''^ and Syncoryne,^'^ the eggs appear upon the external sur- 

 face of the stomach, then fall into the cavity of the mantle, through the 

 openings on the border of which they escape into the water. In the medu- 

 soid individuals of Coryne fritillaria and Coryinorpha nutans, the sexual 

 organs appear to be formed in the angles of the borders of the disc,''^^ and 

 in Cainpanularia in the disc itself. ^ 



§ 52. 



As to the embryonic developments of Polyps, it is probable that in a 

 great number (perhaps all) there is a metamorphosis. 



The development commences by the usual segmentation of the vitel- 

 lus,'^' by which it is ultimately converted into an ovoid, contractile body; 

 this turns upon its longitudinal axis by means of cilia, with which it is en- 

 tirely covered, swimming about like many Infusoria. These embryos, 

 often developed in the mother, have sometimes been taken for swimming 

 eggs.'^^ Afterwards they attach themselves to some body, and usually lose 

 their cilia ; the free extremity of their body opens, allowing the escape of 

 the Polyp, which, in the mean while, has been developed in the interior, 

 with its arms in front. Many of the Polyps thus produced multiply by 

 gemmation, and thus become the foundation of new Polyp-colonies. ^^^ 



1 Wagner (Isis 1833, Taf. XI. fig. 8). 



2 Loven {fViegmami's Archiv. 1837, I. Taf. 

 VI. fig. 19, 20). 



3 Steenstrup, TJeber d. Generationswechsel, p. 

 23, 24. 



1 It is indeed singular that with Hydra the divi- 

 sion of the vitellus takes place before the eggs are 

 either detached from the body, or are surrounded 

 by a dentated envelope. I do not yet know at what 

 epoch the development of the embryo commences, 

 for I have never seen the young come forth. It is 

 impossible for me to say whether or not these 

 Polyps experience a metamorphosis. Pallas (Ka- 

 rakteristik d. Thierpflanzen p. 53) has seen the 

 young Polyps come forth from the egg, but he gives 

 no description. Laurent, also, only says that the 

 young animal escapes formed from the egg, with- 

 out describing the embryo {Froriep^s neue Notizen, 

 No. 513, pi. 101). The segmentation of the vitellus 

 has been observed by Fan Beneden in the eggs of 

 Pedicellina. Sae his Rech. sur I'anat. d. Bryo- 

 zoaires (suite) loc. cit. XIX. p. 18, pl. II. 



'2. As would be inferred from his description, Cav- 

 olini (loc. cit. p. 47, 50, Taf. IV. fig. 7-10 and 13- 

 15) has observed similar embryos to those of Gor- 

 gonia and Madrepora. Ills descriptions of various 

 eggs of Sertularia leave no doubt that they also 



make the matter any more clear ; for, even admit- 

 ting that they are proper ova, it is difltfcult to con- 

 ceive bow the impregnation (of which the segment- 

 ation for a definite result is the sequela) could take 

 place while the ova are thus bui-ied in the capsules. 

 The subject requires further research. See also 

 Steenstrup, Untersuch. ub. Hermaphroditismus, p. 



were embryos (Ibid. p. 56, 80 et seq.). Grant also 

 has taken for eggs the contractile, ovoid embryos 

 of Lobularia digitata, which he has seen issue 

 from the mouth of this animal (Froriep's Notizen 

 1828, No. 440, p. 340). Meyen has well described 

 and figured the cihated epithelium of those of Al- 

 cyonella stagnorum (Isis 1828, p. 1223, Taf. 

 XIV. fig. 4, 5). Lovin has observed the elon- 

 gated embryos of Campanularia genie alata, and 

 has taken the division of the vitellus for a sponta- 

 neous fissuration of the embryos (fViegmann^s 

 Archiv. 1837, I. p. 260, Taf VI. fig. 13, 14). Ac- 

 cording to Rathke, who has seen movable lenticu- 

 ,lar embryos in the stomachs of Actinia, these 

 polyps experience a metamorphosis ( Reise Be- 

 merk. aus Taurien zur Morph. p. 10, Taf. 1, fig. 

 12). 



3 This metamorphosis has already been observed 

 by Cavolini (loc. Cit. p. 261, Taf. VI. fig. 7) with 

 Sertularia racemosa, and more lately by Loweri 

 (loc. cit. p. 261, Taf. VI. fig. 15-17) with Campa- 

 nularia geniculata. There ar£ always developed 

 in the interior of the embryos of Alcyonella stag- 

 norum two Polyps, even before the first have es- 

 caped from the egg ; when the escaped embryo has 

 become fixed, its skin bursts, and the Polyps escape, 

 but are able to return again as into a mouth. 



116, and Hancock, Ann. Nat. Hist. 1850, V. p. 

 282. — Ed. 



* [End of ^ 51. 1 See Schultze {Muller^s Arch, 

 1850, p. 57), who has found with Campanularia 

 seminal capsules corresponding to those for egg- 

 capsules pointed out by Lovin (loc. cit.). — Ed. 



