642 PEOP. w. A. heedmak's eevised 



Alimentary canal at the posterior end of the branchial sac. 



Gonads hermaphrodite. 



Gemmation takes place. 



Life-history complicated by alternation of generations and 

 polymorphism. 



This family contains two genera, which may be distinguished 

 as follows : — 



All the muscles in the form of encircling hoops Dolioluin. 



The musculature reduced to 2 hoops at eacli end and two lateral 

 S-shaped bands Ancliinia. 



DoLiOLUM, Quoy and Gaimard, 1835. 



Body always more or less barrel-shaped, not attached, and 

 never forming a colony. Branchial aperture at the anterior end, 

 atrial at the posterior, both surrounded by lobes. 



Test yerj thin, containing no test-cells. 



Mantle containing well-developed, transversely arranged 

 muscle-bands, which in the fully developed sexual animal are 

 always eight in number. They surround the body like hoops. 



branchial sac usually of moderate size, occupying the anterior 

 half or three-quarters of the body. Its wall contains transverse 

 and fine longitudinal vessels, separated by stigmata, but no 

 internal longitudinal bars, and it is never folded. The stigmata 

 are placed transversely, and vary in number from five to fifty or 

 more on each side of the sac. 



Dorsal lamina and tentacles absent. 



Nerve-ganglion placed in the median dorsal line, a little ante- 

 rior to the middle of the body, and between the third and fourth 

 muscle-bands. 



Dorsal tubercle placed some distance in front of the nerve- 

 ganglion, and surrounded by the spirally-coiled dorsal ends of 

 the peripharyngeal bands. 



Alimentary canal placed ventrally, behind the branchial sac. 



Gonads ventral, opening into the peribranchial cavity near to 

 the anus. 



A tailed larva is formed, which develops into an asexual form, 

 the blastozooid, the buds from which are polymorphic, giving 

 rise to («) nutritive forms, the gastrozooids ; (5) foster-forms, 

 the phorozooids ; and (c) reproductive forms, the gonozooids. 



