CCELENTEEATA. 91 



— FsET n. LEUCKiiiT, Beitriige zm- nliheren Kenntniss wirbelloser Thiere. Braiinscliweig, 1817. 

 —Huxley, On the anatomy and affinities of the family of the Medusae. Phil. Tr. 1849. — 

 Agassiz, L., Contiibutions to the nat. hist, of the Acalephs of N. Am. (Mem. of the Amer. 

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

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



Hydromedusas : Van Benbden, P., Mem. sur les Campanulaires de la cote d'Ostende. (Nouv. 

 M^m. de I'Acad. royale de Braxelles. T. XVII.) Recherches sar I'embryog^nie des Tubulaires 

 (ibid.). — KoLUKEE, Die Schwimmpolypen von Messina. Leipzig, 1853.^Leuckabt, R., Zur 

 nSheren Kemitniss der Siphonophoren von Nizza. Ai-ch. f. Nat. 1851. — Gesekbauh, Beitr. zur 

 naheren Kenntniss der Siphonophoren. Zeitsclir. f. wiss. Zoologie. Bd. V. — Vogt, C, Snr les. 

 Siphonophores de la mer de Nice. M^m. de I'inst. Genevois, 1851. — Glaus, Ueber Physophora 

 hydrostatica. Zeitschr. fiir w. Zoolog. Bd. X. Nene Beobachtungen. Ibid. Bd. XIII. — Hackel, 

 E., Zur Entwiokelungsgesch. der Siphonophoren. Natuurkund. Verhandelingen. P. I. St. C, 

 Utrecht, 1869.— Huxlet, Oceanic Hydi-ozoa. London, 1859. (R.S.)— Fobbes, Ed., A monograph of 

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

 Jenaische Zeitschiift. Bd. I. II. (Also under the title : Beitr. zm' Naturgesch. d; Hydromedusen. 

 I. 1863).— ScHULZE, P. E., Ueber den Bau und die Entwickelung der Cordylophora lacustris. 

 Leipzig, 1871. — The same, Ueber d. Bau v. Syucoryne, etc. Leipzig, 1873. — Kleinenbekg, N., 

 Hydra. Leipzig, 1872. — Allmax, G. J., Monograph of the Gymnolilastic or tubularian Hydroids. 

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

 Phil. Trans. Vol. 165. 



Calycozoa : Clabk, H., Prodi'omus of the History, etc., of the order Lncernaria. Journal of Bost. 

 Soo. of Nat. Hist. 1863. 



Thecomedusoe: Allstan, G. J., On the Structm'e and systemat. position of Stepbanoseyphus 

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



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

 der Ostsee. Abhandl. der Berl. Acad. 1835. — Milne-Edwakds, Ann. sc. nat. III. xvi. — Wagneb, 

 R., Ueber den Bau der Pelagia nootiluca und iiber die Organisation der Medusen. Leipzig, 1811. 

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

 Rhizostoma Cuvieri. Mem. Acad. Imp. des Sc. de St. P(;tersb. VII. Ser. T. XVI. — Gkenacher, 

 H., and Nolo, F. C, Beitr. z. Anatomic u. Systematik der Rhizostomeen. Abh. d. Senckenb. 

 GeseUsch. Bd. X. 



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

 Hollaed, Monogi-aphic anatomique du genre actinia. Ann. sc. nat. III. xv. — Haime, J., Mem. 

 sur le genre Uereanthus. Ann. sc. nat. IV. i. — Lacaze-Duthieks, Hist. nat. du corail. Paris, 

 18C1. — The same, Memoires sur les Autipathaires. Ann. sc. nat. V. ii. iv. Ddveloppement des 

 CoraUiatres. Aj'chives de Zoolog. exp. Vol. I. II. — Kollikee, Die Pennatuliden. Abh. d. 

 Senckenb. GeseUsch. Bd. VII. — Eisen, G., Bidr. tid kilnnedomen om Ronilla. Kongl. Svensk. 

 Vet. Handl. Bd. XIII.— v. Koch, G., Anat. d. Orgelcoralle. Jena, 1871.— Moseley, H. N., 

 On the structm'e and relations of the Alcyonariau Heliopora cwrulea, etc. Phil. Transae. 

 Vol. 166, Pt. L 



Ctenophora: Will, Horo3 tergestinse. Leipzig, 1811. — Milnb-Edwaeds, Ann. sc. nat. S^r. IV. 

 Vol. VII.— KowALEVSKr, A., Entw. des Eippenquallen. Mi^m. de I'Acad. Imp. de St. Petersl). 

 Vli. S^r. Tom. X. — Fol., H., Beitr. z. anatom. Entvvickl. einiger Rippenqnallen. Berlin, 18Q9. 

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



Form of the Body. 

 § 72. 



The forms of body of tlie two great divisions wliich make up 

 tlie 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 

 Avith the other. This stage is permanent in all the Spongiee ; in 

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

 differentiation of transverse axes. 



Among the Spongife the Gastrula attains, when attached by its 



