172 METAMORPHOSES OF MAN 



CHAPTER XVII. 



GENEAGENETIC PHENOMENA OP KADIATA. 



The tliree classes — BcliinoderHiata (sea-urchins, &c), 

 Acalepha3 ( jelly-fish), and Polyps — which collectively 

 constitute the sub -kingdom Radiata, require to be 

 very fully treated, in order to give a detailed account 

 of the varied and complex phenomena presented in 

 their reproduction. Greneagenesis is seen here in all 

 its phases ; and as in many other instances, so in this 

 one, the study of embryogeny, by disclosing unex- 

 pected results, put the history of these beings in an 

 entirely new light, and modified received opinions in 

 many particulars. We have spoken of the Hydra and 

 Aurelia already, and we shall now mention some 

 additional facts in support of this assertion. As an 

 example, we shall select from the arborescent, 

 plant-like polyps which cover our rocks and sea- 

 weeds, the pretty Gampanularia geniculata, whose 

 strange development has been so patiently watched 

 by Lowen ;<* but we shall now and then explain the 

 results arrived at by the Swedish naturalist, f through 

 the assistance of Steenstrup's writings and those of 

 his followers. 



* " Observations sur le Developpement et les Metamorphoses des 

 genres Campannlaire et Syncorne." This work, which was first 

 published in Swedish, was afterwards translated into French and 

 German. — Aimales des Sciences naturelles, 1841. 



t " Uber den Generationwechsel." 



