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 CtenopJwra, 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, Discona/nthe) 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 Eudoj'in 

 and Emcee, 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 Untersuchunycn I. Giessen, 1853. 



The same. Zur ndhcrn Kenntniss dcr Siphonophorcn von Nizza. Arch. ;. 



Nutu/ycschichtc. 1854. 



C. Gegenbaur. Bcolachtungen uber Siphonoplioren. Zeitschr. f. w. ZooL 1853. 

 The same. Neuc Beitrage zur Kenntniss der Siiihonophorcn. Nova acta. Tom. 27. 



1859. 



C. Vogt. Mcmoircs sur les Siphonorjhorcs. M<'ni<iir< * de Vlnstitut genevois. 1854. 

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



1853. 

 Milne-Edwards et J. Haime. Histoire naturelle des Coralliaircs. 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-systematisehc Bcschreibung der Alcyonarien. Die Pennatuliden. 



Abhandlunrjcn Senkenb. nat. Ges. Frankfurt. Bd. 7 and 8. 1872. 

 C. Glaus. Ucbcr Halistemma tcrgestinum. Arbeit. Zool. Institut. Wlcn. 1878. 

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



1871-72. 2 vols. 



N. Eleinenberg. Hydra. Leipzig, 1872. 

 O. and R. Hertwig. Das Nervensystem icnd die Sinncsorgane dcr Medusen. Leipzig, 



1878. 



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

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

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



Neapcl. Leipzig, 1880. 



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

 A. Andres. Monografia delle Attinie. 1. Thcil, In : Fauna und, Flora des Golfes 



von NcajK?. 1S84. 



