104 PROCEEDINGS OF THE AMERICAN ACADEMY 



of which is surrounded by a sheath, most likely of connective tissue. 

 A similar structure was seen by Nasse ('82, p. 13) in Tubifex, and is 

 known to exist in other worms and among the Gastropoda. 



The lateral lines (PI. II. fig. 17) consist of a few cells, occupying the 

 longitudinal space at the middle of the side walls of the body, between 

 the dorsal and ventral halves of the lateral band of longitudinal muscles. 

 They are considered by Biilow ('S3, p. 7.')) to be nervous in function, 

 and their connection with the oesophageal commissures has been traced 

 by Semper in the case of Nais, but in Aulophorus I have been unable 

 to trace them as far forward as the region of the commissures. 



Seginental Organs. 



The segmental organs (PI. I. fig. 8) correspond closely to the de- 

 scription given by Perrier for those of Dero obtusa. Each somite 

 after the sixth or seventh contains a single pair, which begin in the 

 preceding segment and open out through the ventral wall of their own 

 somite. Each organ is a thick-walled tube whose interior is lined by 

 short, fine, vibratile cilia. Its first portion, lying in the anterior of the 

 two segments concerned, is an expanded funnel, the opening of which 

 bears cilia which are much longer than those found elsewhere in the 

 tube. After passing the dissepiment, to which it is attached, there is 

 an elbow-shaped, glandular expansion of the tube. From this expan- 

 sion the tube turns toward the opposite side of the body, and, rising 

 vertically, makes many convolutions, at the same time becoming cov- 

 ered with an irregular granular concretion. Nuclei may be seen in 

 parts of this granular matter, and at times whole cells are visible, so 

 that it is really composed of rounded cells closely applied to the tube 

 and covered with granular matter. Following this cell-covered portion 

 of the tube is a convoluted portion like that following the glandular 

 swelling. The tube finally ends in an expansion which opens to the 

 outer world a little in front of the ventral fascicle of podal stylets. 



Throughout its course the walls of the tube show transverse striae. 

 The cells covering a part of it possibly secrete the glutinous material 

 that forms the basis of the tubes in which the animals live ; but the 

 presence of similar cells in related forms that do not build a tube is 

 opposed to this view, 



LiTKRATL'RE. , 



Biilow, C. 



'83. Die Keimschichton des waclisendcn Schwanzcndc8 von Lunihriculus 



varii'gaius, nebst Beitrtltre zur Anatomie und Histologic dieses Wurines. 



Zeitschr. f. wiss. Zool., Bd. XXXIX. Heft 1, pp. 64-9G, Taf. V. 28 Sept., 



1883. 



