^^ 44, 45. 



THE POLYPI. 



51 



and especially the nature of the soil upon which the colony may have been 

 fixed.=^ <■'> 



§ 44. 



3. It is probable that all Polyps reproduce by eggs. This requires two 

 kinds of organs, one to produce the egg, the other the semen. Both kinds, 

 ovary and testicle, have already been described in many species. 



Their distribution is quite varied. In some, the sexes are united in the 

 same individual/'^ in others they are distinct/-' with the colonial polyps 

 the sexes are separate, and each colony^^' may be composed of individuals 

 which are androgynous, or those of one sex alone.'*' 



Some species are sexless, and remain so ; but they produce by gemmation 

 individuals of a particular character, which have sexual organs.'^' These 

 last, which have usually either a campanulate or discoid form, are separated 

 from the corallum often before the sexual organs have been formed, and 

 ■which they do not acquire until an advanced period of their lives. During 

 thi.i time they swim freely about, like the pulfnograde Acalephae,*^' for 

 ■which, as well as for young Polyps, they are often taken. '^' 



§45. 



That the relations just described really exist, may be learned from the 

 following facts : In Coryne echinata a.nd vulgaris, there are formed at their 

 base, quadrangular and campanulate individuals, which lay numerous 

 eggs.'^' In like manner also, ovigerous capsules are formed about the base 

 of Syncoryne ramosaß^ In Coryne fritillaria,^^^ the new individuals are 

 completely detached and swim freely about, closely resembling Medusae. 

 In this condition they are developed, and their eggs come to maturity,**' 



4 According to Erdl {Froriep^s neue Notizen, 

 1839, No. 249, p. 101) the coralla of Veretillum 

 cynomoTiiivi and A/ci/onium have always either 

 male or female individuals alone. Krohn has 

 perceived the same of Sertularia (Muller's Arch. 



1843, p. 181). 



5 Coryne, Syncoryiie and Campanularia. 



6 Coryne and Campanularia. 



7 Very striking, at least, is the resemblance of 

 Van Benedeti's (M^m. loc. cit. pi. II.) figure of a 

 free ftmale of Campanularia gelatinosa and those 

 of Sam (Beskrivelser. loc. cit. p. 28, Taf. VI. fig. 

 14) of small Acalephae, named by him Cytaeis 

 octopunctata, and by fVill (Horae tergestinae, 



1844, p. 68, Taf. II. fig. 5) as Cytaeis polystyla. 

 1 R. Wagner. Isis, 1833, p. 256, Taf. XI.; also 



Icones zoot. Tab. XXXIV. fig. 16. 



- Lowen. )Viegmann\i Archiv. 1837, I. p. 321, 

 Taf. VI. fig. 19-25. 



3 Steenstriip. Ueber d. Generationswechsel, p. 

 20, Taf. I. fig. 41-47. 



4 According to Sars (Beskrivelser. loc. cit. p. 6, 

 Taf. I. fig. 3), these remärt-s are also true of Co- 

 rymorpha nutans. 



3 Eschara and Fliistra have a lamellated form 

 -when fi.xed to stones, shells, or the broad leaves of 

 Algae ; but are tubular when attached to the 

 ^tems of plants. Alcyonella stagnorum under- 

 ,goes similar changes in the form of its corallum. 

 It divides in a regular dichotomous manner 

 ■(Eichhorn, Beitr. zur Naturgesch. d. kleinsten 

 Thiere. Taf. IV.; also Roesel, loc. cit. Taf. LXXIII. 

 and LXXIV.), and in this form has been described 

 under the name of Plumatella campanulata by 

 Lawarck. But when a colony of these Polyps 

 is fixed upon a stone or a sunken root, they com- 

 mence to be developed in a dichotomous manner. 

 But afterwards they become lapidescent by the 

 liranches of both modes interlacing each other. As 

 the mass becomes more voluminous and dense, the 

 tubes of the dead generation support those of the 

 living. (See Lamouroux, Exposit. method, dtg 

 <jenres de I'ordre des Polypiers, PI. LXXVI. fig. 

 5.) Under this form this IPolyp has received the 

 name of Alcyonella stagnorum (see Raspail, 

 Hist. Nat. de I'Alcyonelle fluviatile).! 



1 Hydra. 



2 Actinia.X 



3 Alcyonella. 



* [End of § 43.] For a fuU account of the 

 reproductive process with Polyps, and the most 

 philosophical exposition of the relations of gem- 

 mation and its analogies and affinities with other 

 developmental processes, see Dana, loc. cit. p. 85. 

 1^0 abstract can be given of such a work. — Ed. 



t [ § 43, note 3. , For full details of the gemmi- 

 parous mode of reproduction with the Bryozoa, 

 see Van Beneden (Recherch. sui- Torganis. des 



Laguncula, &c., Mem. Acad. Koyale de Bruxelles, 

 XVIII. ; also, Recherch. sur I'Anat. la Physiol, 

 et le developpement des Bryozoaii'es, &c. Ibid. 

 XIX.). See also Allman, Report Brit. Assoc. 1850, 

 p. 320. — Ed. 



]: [ § 44, note 2.] According to my own obser- 

 vations, the Actiniae have both individuals which 

 are hermaphrodites and those of one sex alone. 

 — Ed. 



