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MONOGRAPH 



ON 



THE CIRRIPEDIA. 



INTRODUCTION. 



I should have been enabled to have made this Volume 

 more complete, had I deferred its publication until I had 

 finished my examination of all the other known Cirri- 

 pedes ; but my work would thus have been rendered 

 inconveniently large. Until this examination is com- 

 pleted, it will be more prudent not to discuss, in detail, 

 the position of the Lepadiclse amongst the Cirripedia, or 

 of these latter in the great class of Crustacea, to which 

 they now, by almost universal consent, have been 

 assigned. I may, however, remark that I believe the 

 Cirripedia do not approach, by a single character, any 

 animal beyond the confines of the Crustacea : where such 

 an approach has been imagined, it has been founded on 

 erroneous observations ; for instance, the closed tube 

 within the stomach, described by M. Martin St. Ange 

 (to whose excellent paper I am greatly indebted), as 

 indicating an affinity to the Annelides, is, I am con- 

 vinced, nothing but a strong epithelial lining, which I have 

 often seen ejected with the excrement. Again, a most 

 distinguished author has stated that the Cirripedia differ 

 from the Crustacea: — 1st. In having "a calcareous shell 

 and true mantle;' but there is no essential difference, as 



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