82 



CRUSTACEA CIRKIPEDIA 



The body of the adult Lepas is retracted into the mantle, 



MO 



!FlG. 50. — Cypris-stage in the development of Lp.pas australis, x 15. A^ Peduncle : 

 -1. J/, adductor muscle ; C, caecum of oesophagus ; C.g, cement-glands ; CV, cirri 

 (thoracic appendages) ; £", compound eye ; H^, simple eye ; O, ventral ganglia ; 

 /, intestine ; M, month ; Jl/.C, mantle-cavity ; 0, ovary ; >S, stomach, (After 

 Hoek. ) 



and lies free in the mantle-cavity, but is continuous anteriorly 

 with the tissues of the peduncle, into which 

 the mantle does not extend. The thorax, 

 with its six pairs of legs, can be protruded 

 from the mantle-cavity through the slit- 

 like opening which separates the two valves 

 of the mantle along the ventral middle line ; 

 and when the animal is feeding, the thoracic 

 legs are so protruded, and by their concerted 

 waving action they drive the food-particles 

 in the water along the channel between 

 them, itntil the particles reach the oral 

 cone, where they are masticated by the 

 mandibles and two pairs of maxillae, and 

 so passed into the alimentary canal. When 

 the animal is disturbed it rapidly retracts 

 its limbs, the valves of the mantle are 

 closed by means of a strong adductor muscle 

 in the head, and the animal is protected 



from all external influences. In the acorn-barnacles (Operculata), 



M 1 



Fig. 51. — Pupa of Lepas 

 pectinata, x 8. A, An- 

 tenna ; (7, carina ; M, 

 adductor muscle ; S^ 

 scutum ; T, tergum. 

 (After Gruvel.) 



