EPIZOA AND CIRRIPEDIA. 267 



taiieous fission ; and the individuals so produced developing the 

 ordinary organs of generation. 



The low organised articulated classes, which succeed the Anellids 

 in the rising progress, undergo such extraordinary metamorphoses 

 before attaining their mature state, as to mask their true relations, 

 not only to the class, but to the primary division of animals to which 

 they belong. This is especially the case with the creatures whose 

 organisation and development will form the subject of the present 

 Lecture. 



This elongated, cylindrical, unarticulated Lerna^a {fig. 112), whose 

 smooth soft body seems devoid of any other appendages than the two 



^^ 113 



112 .^fe'^ 



Peniculus fistula. a 



Balanus sulcatus. 



long slender ovisacs (/), might be regarded, on the fall of these de- 

 ciduous appendages, as one of the entozoa of the fish to which it is 

 attached, and on the nutrient juices of which it subsists. 



This Ballanid {fig. 113), imprisoned in its conical calcareous shell, 

 and cemented to the stone on which it grew, might seem as naturally 

 to belong, like its neighbour the limpet, to the testaceous Mollusca. 



How minute and accurate must have been the investigation of the 

 forms and structures of these animals, at every stage of their exist- 

 ence, before the truth began to dawn, that they were more nearly 

 allied to one another than to any other class of animals ! The most 

 vivid imagination of the boldest generaliser or sjieculator upon the 

 unity of organisation in the Animal Kingdom could never have di- 

 vined that the Lernjca and the Cirriped were at one period of their 

 lives locomotive animals, swimming about under very similar forms, 

 and by almost identical natatory instruments, — not under the com- 

 mon ciliated infusorial form, in which the Polype, Acalephe, Echino- 

 derm and certain Entozoa, Anellids, and Mollusks, first enter into 

 active life, — but with symmetrical pairs of jointed setigerous legs like 

 those of the full-grown errant Anellids and the lower organised 

 Crustaceans, to which the Epizoa and Cirripedia are, in fact, essen- 

 tially and most closely allied, although they end their career as 



