There is no armed protrusible pharynx, such as exists in some other Chaetopods.
This may be associated with mud-eating habits; but it is not wholly certain that this is the case; for in Chaetogaster and Agriodrilus, which are predaceous worms, there is no protrusible pharynx, though in the latter the oesophagus is thickened through its extent with muscular fibres.
The male ducts are either one pair or two pairs, which open by a common and complicated efferent terminal apparatus furnished with a protrusible penis.
Each testis communicates by means of an efferent duct with a common collecting duct of its side of the body, which opens on to the exterior by means of a protrusible penis, and to which is sometimes appended a seminal vesicle.
- A protrusible proboscis exists, but there are no jaws.
Lankester as a branch of the Cephalopoda, chiefly on account of the protrusible suckerbearing processes at the anterior end of Pneumonoderma.
Piercing jaws modified and reduced, a tubular, protrusible suckingtrunk being developed; mouth with hooks.
The body is ringed, and often has circles of spines, which are continued into the slightly protrusible pharynx.
Thus in the recently discovered arctic genus Prosorhynchus the muscular and glandular extremity is protrusible, but in the allied Gasterostomum this organ is represented by a sucker with fimbriated or tentacular margins.
The body is divided into eleven segments and the protrusible proboscis apparently into two, and the cuticle of the central segment is thickened to form three plates, one dorsal and two ventrolateral.
The male organs are usually a testis, a large seminal bladder and a protrusible penis.
The male organs consist of paired testes communicating by delicate canals with a protrusible penis.
From this junction there proceeds an oviduct or " uterus " (paired or single) which before opening to the exterior expands to form a muscular protrusible pouch - the bursa copulatrix.
Itura, for example, belonging to the former, has protrusible scent-emitting processes at the end of the abdomen; and Thyridia has scent-producing tufts of hair on the edge of the posterior-wing.
In the male there are a right and a left protrusible penis in every genital segment, into which opens the nephridium and a sperm-sac. The wide funnels of the nephridia of this region are possibly of coelomic origin.
The eggs are laid in the spring as a rule, and after about a week they give rise to a minute, ringed larva with a protrusible boring apparatus consisting of three chitinous rods.
The genus Rana may be defined as firmisternal Ecaudata with cylindrical transverse processes to the sacral vertebra, teeth in the upper jaw and on the vomer, a protrusible tongue which is free and forked behind, a horizontal pupil and more or less webbed toes.
The mouth is anterior and slightly ventral; it leads into a protrusible pharynx armed with recurved teeth that can be everted.
The former leads to a protrusible pharynx (B), from which the oesophagus opens into a wide intestinal chamber with branching lateral diverticula.
The terminal part of the male ducts may be protrusible and act as an intromittent organ, or this function may be discharged by some of the appendages, as, for instance, in the Brachyura.