400 



INVERTEBRATE MORPHOLOGY. 



most part of the stalk are the two scuta (sc), while above 

 these are the terga {te), also paired, the opening into thte in- 

 terior lying between the terga and the scuta of opposite sides. 

 In Scalpellum between the two scuta a sixth, unpaired, piece, 

 the rostrum, is inserted, and in the same genus between the 

 scuta, terga, and carina a,nd the summit of the stalk small 

 accessory pieces occur ; and if one imagines a disappearance 



Fig. 181. — Lepas fascicular is. A, exterior; B, structure. 



ag = antennary gland. 

 Car = carina. 

 Cir = cirrus 

 M = shell-muscle. 

 Od = oviduct. 



Ov = ovary. 

 pe = peduncle. 

 8c = scutum. 



t = testis. 

 Te = tergum, 

 Vd = vas deferens. 



of the stalk of such a form, an enlargement of these accessory 

 pieces, usually six in number, and their articulation to form 

 a wall-like circle around the body of the animal, the scuta 

 and terga closing it in and forming as it were a roof, an idea 

 of the arrangement of the shell of Balanus, the acorn-barnacle, 

 will be obtained. 



No special respiratory organs exist, the entire surface of 

 the body probably performing this function, nor does a heart 

 seem to occur in any member of the group. The nervous 



