344 Introduction to Animal Morphology. 



stomach is small, with hepatic caeca at its pylorus, and 

 with two small, lobed, anterior glands, which may be 

 salivary. The anus is between the two hindermost pair 

 of cirri. The heart is a simple, tubular, dorsal vessel, 

 with an anterior sinus longitiidinalis (Martin St. Ange\ 

 but the peripheral circulation is lacunary ; respiration 

 is dermal, or in some Lepadidae by lancet-shaped gills, 

 or in Balanidae by folds of the mantle lining. The 

 larvae possess simple eyes, which disappear at the 

 first moult after the animal becomes sessile. 



There are pigmy eye-bearing, saccular males, con- 

 taining no organ but a testis, straight cirri, and adhe- 

 sive antennn', sometimes lodged in transverse pits in 

 tlif shell of the female (Scalpellum). The young are 

 minute Nanplii\ free, oceanic, at first oval, pointed 

 behind, with one or two pair of antennae ; the mantle 

 layers then begin to form on each side, and the Nau- 

 plius becomes a cypris-like Pitfa, which at the fourth 

 moult becomes sessile, inclosed in the mantle ; at the 

 fifth moult eyes and antennae disappear as such, being 

 completely modified, the mantle calcifies, and addi- 

 tional abdominal limbs form, which develop into the 

 cirri, while the mouth appendages and the post abdo- 

 men develop. Cirripedes are marine, found on stones, 

 ships, and as oikosites on whales, fish, mollusca, &c. 

 About 100 living species are known. 



They arv divided into four orders : 



i. Thoracica (Danvin) stalked or sessile, with six cirri- 

 ferous segments ; a rudimental abdomen with post abdominal 

 appendages ; labrum not separately movable ; pupa dodeca- 

 pod. This contains three families : i. Lepadidae, Barnacles 

 peduncle containing the ovary and cement gland ; shell late- 

 rally compressed, trigonal, with rounded angles, with (Lepas) 



