210 



CRUSTACEA. 



the lateral angles 

 of its frontal mar- 

 gin, is produced 

 out to form the 

 " frontal horns " 

 (h). The posterior 

 end of this dorsal 

 shell appears at 

 first to be rounded, 

 but at a later stage 

 may have a pair 

 of spines directed 

 backwards and 

 upwards. Each 

 of the frontal 

 horns contains a 

 style-like process 

 (Claus, No. 8), 

 while in the sheath 

 that covers this 

 are found the 

 openings of two 

 large and several 

 smaller unicellular 

 glands (Fig. 102 

 B, dr, Claus, No. 



8; WlLLEMOES- 



SuHM, No. 62). 

 This is probably 

 a protective appa- 

 ratus and not a 

 sensory organ. 

 The posterior end 

 of the body (tho- 

 raco-abdominal 

 section. Fig. 102 

 ^,/) projects freely 

 out beyond the 



Pio. 102. — Larval stages of Balanus (after Claus). A, older NaupUus stage. B, Metanauplins. 

 ft', first, a", second antenna; af, anus; dr, glandular cells of the frontal horns; ds, dorsal 

 caudal spine ; f l-fy^, lirst six pairs of thoracic limbs ; fs, frontal sensory organ ; h, frontal 

 liorns; ind, mandible; mx, rudiment of the maxilla; ol, upper lip; t, tlioraco-abdominal 

 appendage. 



