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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 65. 



are present in the sectioned half of the worm and are slightly dorsad 

 of h in 11, 12, and 13. Corresponding pores are doubtless present on 

 the unsectioned half of the worm, although they are not recognizable 

 because of their small size. The oviducal pores are on 14 and are a 

 little anterior to and slightly dorsad of h. The spermathecal pores 

 are paired in 7/8 and 8/9 and are slightly ventrad of seta line cd. 

 Internal characters. — The structure of the body wall differs from 

 that more commonly found in earthworms. The circular and longi- 

 tudinal muscle layers are separated by an intervening layer of tissue 

 of an entirely different nature (figs. 1 and 4). It is not stained by 

 the hematoxylin or eosin used, and hence in the sections is sharply 

 differentiated in color as well as in structure. The thickness of the 

 layer is about equivalent to that of the layer of circular muscle 

 fibers. In section it has a very distinctly laminated appearance, there 

 being more commonly four to six laminae, which become much re- 

 duced in thickness opposite the intersegmental grooves. Similar 

 conditions are found in sections of a specimen of Drawida hournei 



Michaelsen, for 

 which we are in- 

 debted to Doctor 

 Michaelsen, an d 

 which is the only 

 material of the 

 family available 

 for comparison. 

 A detailed histo- 

 logical study of 

 this tissue has not yet been attempted by us, but there is no indica- 

 tion of its being fibrous, as the transverse and longitudinal sections 

 present much the same appearance. 



Septa 5/6-7/8 (fig. 2) are very strongly thickened and the ones 

 posterior to 7/8 are extremely thin and delicate. Those between 7/8 

 and 13/14 are so extensively displaced and obscure that the exact 

 determination of the internal boundaries of the somites and the 

 assignment of the contained organs to their proper somites is 

 rendered somewhat difficult. What is assumed to be septum 8/9 

 joins the dorsal wall at 10/11 and the ventral wall at the 

 middle of 10, as indicated by the external metamerism and the 

 setae. Septum 13/14 is attached to the body a little way pos- 

 terior to 13/14, as indicated by the intersegmental groove. Be- 

 tween septa 8/9 and 13/14 there seem to be but two septal layers con- 

 necting with the body wall, although there are evidences of more 

 septa among the organs. The anterior one of these two layers is 

 perhaps the combined septa 9/10, 10/11, and 11/12 and jmns the 

 mid- ventral body wall at about the middle of 12 and the mid-dorsal 



n c 



Fig. 2.— Syngenodrilus lamuensis. Anterior end from which piece 



WAS REMOVED FOR SECTIONING. X5. g, GIZZARD; n C, NERVE CORD; 

 7/8, SEPTUM BETWEEN 7 AND 8. 



