DEFINITION 



199 



Australia. It would be unfair not to record here the invaluable 

 services of the late Thomas Bolton, 

 and his son of the same name, 

 both of Birmingham, and of J. 

 Hood of Dundee, who have found 

 and widely distributed living 

 specimens of new, rare, and in- 

 teresting species. 



Definition of the Class. We 

 may define Botifera as a class of 

 minute bilaterally symmetrical 

 animals, with a chitinous integu- 

 ment, a soft terminal " disc " 

 fringed by a complex ciliary 

 " wreath," an anterior or sub- <*? 

 ventral mouth, and a dorsal 

 cloacal aperture, beyond which 

 the body is usually prolonged into 

 the " foot " or process 

 cement glands, and ser 

 attachment, temporary or perma- 

 nent. The body-cavity has no 

 epithelial lining, and is traversed 

 by nerves and muscles. The 

 alimentary canal possesses a chit- 

 inous gizzard or mastax of pecu- 

 liar arrangement, and it usually 

 opens into a cloaca. The nervous 



Centre Consists of a ganglion 011 Fig. 106. Hydatina senta, ventral view. 



the dorsal Side of the pharynx, to (fter Plate.) al Lateral antenna ; 



r J > U, bladder ; ci, cmgulum ; e, e, eggs 



which a Second One On the veil- in uterus ;fg, loot gland ; g, gizzard ; 



tral side is sometimes connected 

 to form a complete ring ; eyes 



bearing 



ing for 



and bristle -bearing feelers are 



gg, gastric gland ; gm, gerniariuni or 

 ovary ; gr, ciliated lobes of " groove " ; 

 i, intestine ; k, k, kidneys ; m, mouth ; 

 ns, nephrostome ; oe, oesophagus ; re, 

 reual commissure, transverse tube unit- 

 ing kidneys above mouth ; s, stomach 

 overlaid by reproductive organs ; tr, 

 trochus ; u, uterus ; vm, vitellarium 

 or yolk-gland. 



usually present as 



A paired system of renal tubes 



serves for excretion, opening 



through a median contractile 



bladder into the ventral side of the cloaca. The sexes are distinct ; 



but the males (Fig. 107), which mostly lack digestive organs, occur 



