CCELENTERATA. 91 



— Feet n. Leuckaet, Boitriige zur naheren Kcnntniss wirbelloser Thicrc. Braunschweig, 1817. 

 — Huxley, Ou the anatomy and affinities of the family of the Medusas. Phil. Tr. 18-19. — 

 Agassiz, L., Contributions to the nat. hist, of the Acalcphse of N. Am. (Mem. of the Amor. 

 Acad, of Arts and Sc. Cambridge, 1850).— The same, Contrib. to the nat. hist, of the United 

 States of North America. Vol. III. IV. 1860-62. 



Hydromedusaj : Van Benbden, P., Mem. sur les Canipanulaires de la cute d'Ostende. (Nouv. 

 Mem. de l'Acad. royale de Bruxelles. T. XVII.) Recherches sur l'embryogenie des Tubulaires 

 (ibid.). — Kollikeb, Die Schwinimpolypen von Messina. Leipzig, 1853. — Leuckaet, R., Zur 

 naheren Kcnntniss der Siphonophoren von Nizza. Arch. f. Nat. 1851. — Gegenbaur, Beitr. zur 

 naheren Kenntniss der Siphonophoren. Zeitschr. f. wiss. Zoologie. Bd. V. — Vogt, C, Sur les. 

 Siphonophores de la mer de Nice. Mem. de l'inst. Genevois, 1851. — Claus, Ueber Physophora 

 lrydrostatica. Zeitschr. fur w. Zoolog. Bd. X. Neue Beobachtungen. Ibid. Bd. XIII. — Hackel, 

 E., Zur Entwickelungsgesch. der Siphonophoren. Natuurkund. Verhandelingen. P. I. St. 0, 

 Utrecht, 1809. — Huxley, Oceanic Hydrozoa. London, 1859. (R.S.) — Fobbes, Bd., A monograph of 

 the British naked-eyed Medusa?.. London, 1818. (R.S.) — Hackel, Die Familie der Riisselquallen. 

 Jenaische Zeitschrii't. Bd. I. II. (Also under the title : Beitr. zur Naturgesch. d. Hydromedusen. 

 I. 1865). — Schxlze, F. E., Ueber den Bau unci die Entwickelung der Cordylophora lacustris. 

 Leipzig, 1871.— The same, Ueber d. Bau v. Syncoryne, etc. Leipzig, 1873.—' Kleinenbebg, N., 

 Hydra. Leipzig, 1S72. — Alliian, G. J., Monograph of the Gymnoblastic or tubularian Hydroids. 

 P. I. and II. London, 1871-72. (R.S.)— The same, On the structure and develop, of Myriothela. 

 Phil. Trans. Vol. 165. 



Calvcozoa : Clark, II., Prodromus of the Historv, etc., of the order Lucernavia. Journal of Bost. 

 Soc. of Nat. Hist. 1S03. 



Thecomedusa?: Allmax, G. J., On the Structure and systemat. position of Stephanoscyphus 

 mirabilis. Trans. Linn. Soc. Sec. ser. Vol. I. Zool. 



Discophora : Ehrexberg, Ueber Acalephen des rothen Meeres und d. Organismus der Medusen 

 der Ostsce. Abhandl. der Berl. Acad. 1835. — Milne-Edwards, Ann. sc. nat. III. xvi. — Wagner, 

 R., Ueber den Bau der Pelagia noctiluca und fiber die Organisation der Medusen. Leipzig, 1811. 

 — Hackel, E., Ueber die Crambessiden. Zeitschr. f . wiss. Zoolog. Bd. XIX. — Brandt, A., Ueber 

 Rhizostoma Cuvieri. Mein. Acad. Imp. des Sc. de St. Petersb. VII. Ser. T. XVI. — Geenacher, 

 H., and Nolc, F. C, Beitr. z. Anatomie u. Systematik der Rhizostomeen. Abh. d. Senckenb. 

 Gesellsch. Bd. X. 



Anthozoa: Ehrexberg, Die Corallenthiere des rothen Meeres. (Abh. d. Berl. Acad., 1832). — 

 Hollard, Monographic anatomique du genre actinia. Ann. sc. nat. HI. xv. — Haijie, J., Mem. 

 sur le genre Cereanthus. Ann. sc. nat. IV. I. — Lacaze-Dcthiers, Hist. nat. du corail. Paris, 

 1861. — The same, Memoires sur les Antipathaires. Ann. sc. nat. V. n. iv. Developpement des 

 Coralliaires. Archives de Zoolog. exp. Vol. I. II. — Kollikee, Die Pennatuhden. Abh. d. 

 Senckenb. Gesellsch. Bd. VII. — Eiben, G., Bidr. tid kannedomen om Renilla. Kongl. Svensk. 

 Vet. Hand]. Bd. Xni.-v. Kocn, G., Anat. d. Orgelcoralle. Jena, 1871.— Mose ley, H. N., 

 On the structure and relations of the Alcyonarian Heliopora can-ulea, etc. Phil. Transac. 

 Vol. 166, Pt. I. 



Ctenophora: Will, Horn? tergestina?. Leipzig, 1811. — Milne-Edwards, Ann. sc. nat. Ser. IV. 

 Vol. VII.— Kowalevsky, A., Entw. des Rippenquallen. Mem. de l'Acad. Imp.de St. P^teivb. 

 VII. Ser. Tom. X. — Fol., H., Beitr. z. anatom. Entwickl. einiger Rippenquallen, Berlin, 18C9. 

 — Eimeb, Th., Zoologische Studien auf Capri I. Ueber Beroe ovatus, 1873. 



Form of the Body, 

 § 72. 



The forms of body of the two great divisions which make up 

 the Coelenterata are alike in the lowest stage ; in that stage, namely, 

 which has been already (§ 28) called the " Gastrula," on account 

 of the development of an enteric cavity. This form represents a 

 larval stage, in which an investment of cilia function as a locomotor 

 organ, and which may fairly be regarded as the common funda- 

 mental form of the two chief divisions of the Zoophyta. In this 

 form only one axis, the primary, can be made out ; it extends 

 from the oral to the aboral pole. The secondary axes are indif- 

 ferent, for all the transverse axes drawn perpendicularly through the 

 primary, at any angle whatsoever, are completely equivalent one 

 with the other. This stage is permanent in all the Spongige ; in 

 the Acalepha3 it passes on into a condition which is characterised by 

 differentiation of transverse axes. 



Among the tSpongire the Gastrula attains, when attached by its 



