NO. 1 hartman: goniadidae, glyceridae, nephtyidae 59 



stable character, such as the structure of the setae, appears to be too 

 uniform throughout the genus to have differential value. The form of 

 the 4 large, horny paragnaths attached to the distal end of the pro- 

 boscis is sometimes specific for the embedded aileron, but requires dis- 

 section to verify its nature. The kinds of parapodial branchiae, if present, 

 are also useful but these organs are sometimes highly extensile or re- 

 tractile, and may vary further with age of individuals, or be subject 

 to environmental fluctuations. 



Another feature that has been found to be highly specific in the 

 species investigated, concerns the minute and numerous organs of the 

 proboscis. These parts are discussed more fully below. The gross struc- 

 tures of the proboscis are well known but the functions of the various 

 parts have been differently interpreted. Thus, the distal jaws or para- 

 gnaths have been generally regarded as organs for capture of food. The 

 circlet of terminal papillae are usually regarded as sensory in function. 

 There is uncertainty regarding the 4 large glands near the embedded 

 paragnaths, but they have been named poison glands (Ehlers, 1868, p. 

 643). The very numerous proboscidial organs that more or less com- 

 pletely cover the epithelium have usually been called papillae, but since 

 they are herein shown to have a terminal or subterminal pore, the term 

 may be inapt. Both pore and canal have been observed, but their re- 

 lations or significance have remained doubtful. 



The successive layers of the proboscis, in cross section (textfig. 3) 

 are most clearly demonstrated on the everted organ. The proboscis is 

 then seen to consist of a double tube composed of outer and inner cylin- 

 ders. They are separated from each other by the inner coelomic space. At 

 the distal end they are connected to each other by the membranes that 

 bound the paragnaths. At the proximal end they connect with the sheath 

 that bounds the mouth on the outside and the proximal end of the 

 alimentary tract on the inside. These inner and outer cylinders resemble 

 each other except that the outer one is covered with proboscidial organs 

 (called papillae by some authors) and the inner one is smooth. Each 

 layer is overlain by a cuticular epithelium. This covers a layer of con- 

 nective tissue penetrated by nerve ganglia and plexuses. The longi- 

 tudinal muscles forming 18 bands (textfig. 3) are separated from one 

 another by narrow strands of connective tissue. Within is a continuous 

 cylinder of circular muscles and finally the peritoneal lining of the 

 coelomic cavity. The layers of the inner cylinder are similar to those of 

 the outer, but in reverse order (Oppenheimer, 1902). 



