Alimentary canal rarely coiled, occasionally with glands which are simple caeca and sometimes serve as air reservoirs; jaws often present and an eversible pharynx.
Each cansists of an eversible hollow tentacle provided with hooklets and capable of introversion within a mem The excretory organs consist of flame-cells, richly convoluted canaliculi, and a pair of longitudinal canals leading to the exterior by one or more pores.
From this point a glandular tube runs to the genital atrium and during the last part of its course is converted into an eversible hooked "cirrus" or penis.
Parapod.ia hardly projecting; palps of prosomium forming branched gills; no pharynx or eversible buccal region; no septa in thorax, septa in abdomen regularly disposed.
The buccal region is unarmed and not eversible.
The distal extremity of this apparatus is sometimes eversible as a penis.
The eversible sacs on the abdominal segments are shown, some protruded and some retracted.
The first of these usually carries a ventral tube, furnished with paired eversible sacs which assist the insects in walking on smooth surfaces, and perhaps serve also as organs for breathing.
There is no reason in the actual significance of the word why the term " proboscis " should be applied to an alternately introversible and eversible tube connected with an animal's body, and yet such is a very customary use of the term.