414 



CRUSTACEA ENTOMOSTRACA. 



a H , 07 



FlO. 268. a, Late nauplius, b, metanauplius larva of Balanus 

 before the moult. Beneath the skin are the rudiments of the 

 lateral eyes (0) and all the appendages F< : to F ri of the cypris 

 stage ; A anus ; A', A" 1st and 2nd antennae ; A' the antennae 

 with suctorial disc ; D intestine ; Dr gland cells of the 

 anterior horns ; Ff frontal filament ; H frontal horns ; Mdf 

 mandibular foot (third pair of appendages) ; MX rudiment of 

 maxilla ; 0' unpaired eye ; 01 proboscis with mouth. (From 

 Claus.) 



The Cirripeds 

 were included by 

 the older natural- 

 ists in the Mol- 

 lusca,to the Lamel- 

 libranch group 

 of which the 

 bivalve shell of 

 the Lepadidae 

 with its calcareous 

 plates and the 

 siphon - 1 i k e 

 peduncle give this 

 division a certain 

 external r e s e in - 

 blance. 



Their relation- 

 ship to the Crus- 

 tacea was fi r s t 

 demonstrated by 

 J. V. Thompson, 

 by the discovery 

 in the year 1829 

 of the nauplius 

 larva of Balanus. 

 The monograph of 

 the Cirripedia by 

 Charles Darwin 

 (Ray Society 

 1851-53) first 

 placed our know- 

 ledge of the struc- 

 ture of the group 

 on a satisfactory 

 basis. 



The structure 

 of the adult 

 Cirripedes, as well 

 as the natural 

 affinities of the 



