ii CNIDARIA LITERATURE 117 



morphosis. Development with alternation of generations and without 

 it can occur in the same species. 



In Corals a free-swimming larva is produced from the fertilised 

 egg, and this attaches itself and develops into a Coral, which either 

 remains a single individual or produces a Coral -stock by means of 

 gemmation and incomplete fission. 



The Ctenophora, without exception, develop direct. 



From the fertilised egg of the Siphonophora a medusoid organism 

 arises, which, by budding, yields the polymorphic animal stock. Here 

 also (Physalia, Disconanthe) the medusoid gonophores can detach them- 

 selves from the stock and lead a free life as sexual individuals. In 

 many Siphonanthe groups of persons, the already mentioned Eudoxice 

 and Erscece, detach themselves from the stock, and swim about freely 

 as minute new animal stocks. In their gonophores the sexual pro- 

 ducts are developed. From the fertilised egg a medusoid organism 

 arises, which by gemmation again becomes the polymorphic animal ] 

 stock. We thus have here again to do with a sort of alternation of 

 generations. 



Literature. 



R. Leuckart. Zoologische Untersuchungen I. Giessen, 1853. 



The same. Zur ndhern Kenntniss der Siphonophoren von Nizza. Arch. f. 



Naturgeschichte. 1854. 



C. Gegenbaur. Beobachtungen uber Siphonophoren. Zeitschr. f. w. Zool. 1853. 

 The same. Neue Beitrdge zur Kenntniss der Siphonophoren. Nova acta. Tom. 27. 



1859. 



C. Vogt. Memoires sur les Siphonophores. Memoires de VInstitut genevois. 1854. 

 A v. Kolliker. Die Siphonophoren oder Schwimmpolypen von Messina. Leipzig, 



1853. 

 Milne-Edwards et J. Haime. Histoire naturelle des Coralliaires. 3 vols. Paris, 



1857-60. 



Th. Huxley. The Oceanic Hydrozoa. Roy. Society. London, 1859. 

 De Lacaze-Duthiers. Histoire naturelle du corail. Paris, 1864. 

 Th. Hincks. Natural History of the British Hydroid Zoophytes. 2 vols. London, 



1868. 

 Kolliker. Antomisch-systematische Beschreibung der Alcyonarien. Die Pennatuliden. 



Abhandlungen SenTcenb. nat. Ges. Frankfurt. Bd. 7 and 8. 1872. 

 C. Glaus. Ueber Halistemma tergestinum. Arbeit. Zool. Institut. Wien. 1878. 

 G. J. Allman. A Monograph of the Gymnoblastic or Tubularian Hydroids. London, 



1871-72. 2 vols. 



N. Kleinenberg. Hydra. Leipzig, 1872. 

 0. and R. Hertwig. Das Nervensystem und die Sinnesm-gane der Medusen. Leipzig, 



1878. 



The same. Die Actinien. Jen. Zeitschr. f. Natumuiss. Bd. XIII. u. XIV. 1879-80. 

 R. Hertwig. Ueber den Bau der Ctenophoren. Jena, 1880. 

 C. Chun. Monographic der Ctenophoren. In: Fauna und Flora des Golfes von 



Neapel. Leipzig, 1880. 



E. Haeckel. System der Medusen. Jena, 1880, 1881. 

 A.Andres. Monografia delle Attinie. 1. Theil, In : Fauna und Floi^a des Golfes 



von Neapel. 1884. 



