MOUTH-PARTS OF THE OYPRIS-STAGE OF BALANUS. 275 



and fifth pairs of appendages of the typical Crustacean 

 series. 



This conclusion is quite in harmony with that of Nussbaum, 

 as deduced from his beautiful anatomical investigations of the 

 adult Cirripede, '' Die Anorduung der Musculatur spricht 

 dafiir, dass jeder der drei Kiefer aus einem Beinpaare hervor- 

 gegangen ist" (No. 11). 



In the fate of the mandibles of the Nauplius and in the 

 constitution of the head of the adult the Cirripedia thus con- 

 form to what is recognised as typical among other Crustacea. 



Bibliography. 



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 1863. 



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 vol. clxvi, 1876. 



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