$$ 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. Durin 
this time they swim freely about, like the, pulmograde 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 echinataand 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 ramosa.” 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.” 
8 Eschara and Flustra have a lamellated form 
when fixed to stones, shells, or the broad leaves of 
Algae; but are tubular when attached to the 
stems 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. [V.; also Roesed, loc. cit. Taf. LX XIII. 
and LXXIV.), and in this form has been described 
ander the name of Plumatella campanulata by 
Lamarck. 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 b lapid it by the 
4 According to Erdi (Froriep’s neue Notizen, 
1839, No. 249, p. 101) the coralla of Veretillum 
cynomorium and Alcyonium have always either 
male or female individuals alone. Krohn has 
perceived the same of Sertularia (Muller’s Arch. 
1843, p. 181). 
5 Coryne, Syncoryne and Campanularia. 
6 Coryne and Campanularia. 
7 Very striking, at least, is the resemblance of 
Van Beneden’s (Mém. loc. cit. pl. II.) figure of a 
free female of Campanularia gelatinosa and those 
of Sars (Beskrivelser. loc. cit. p. 28, Taf. VI. fig. 
14) of small Acalephae, named by him Cytaets 
~pranches 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 Lamourour, Exposit. méthod. des 
Genres de Pordre des Polypiers, Pl. LXXVI. fig. 
5.) Under this form this Polyp has received the 
name of Alcyonella stagnorum (see Raspail, 
Hist. Nat. de ’Alcyonelle fluviatile).f ‘ 
1 Hydra. 
2 Actinia. 
‘8 Alcyonella. 
* [End of § 43.) For a full account of the 
weproductive 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. 
No abstract can be given of such a work. — Ep. 
t [§ 48, note 3., For full details of the gemmi- 
P mode of reprod with the Bryozoa, 
see Van Beneden, (Recherch. sur l’organis. des 
top tata, and by Will (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. 
2 Lowén. Wiegmann’s Archiv. 1837, I. p. 321, 
Taf. VI. fig. 19-25. 
8 Steenstrup. Ueber d. Generationswechsel, p. 
20, Taf. I. fig. 41-47. 
4 According to Sars (Beskrivelser. loc. cit. p. 6, 
Taf. I. fig. 3), these remaris are also true of Co- 
rymorpha nutans. 
Laguncula, &c., Mém. Acad. Royale de Bruxelles, 
XVII. ; also, Recherch. sur |’Anat. la Physiol. 
et le développement des Bryozoaires, &c. Ibid. 
XIX.). See also Aliman, Report Brit. Assoc. 1850, 
p. 320. — Ep. 
+ (§ 44, note 2.] According to my own obser- 
vations, the Actiniae have both individuals which 
are hermaphrodites and those of one sex alone. 
— Eb. 
