Anatomy and Histology of a New Eart/ncorm. 51 



of each fossa, one opening, thus, beside each pair of copulatory 

 setoe on somites 18 and 20. The vasa deferentia open on two 

 very small papillae, one in each fossa near the middle of somite 

 19. The vasa are in no way connected with the prostate 

 glands. Between the fosste the body-wall is a little impressed, 

 and forms here a shallow basin. 



The Dissepiments. 



No dissepiments are present, apparently, between the four 

 most anterior somites. The first developed partition separates 

 somites 5 and 6, It is much thinner than the five succeeding 

 ones. The latter are greatly thickened from the unusual de- 

 velopment within them of muscle fibers. These six anterior 

 dissepiments, and to some extent those immediately following, 

 project backwards from the line of attachment to the body- 

 wall, so that anterior septa are received into succeeding ones, 

 and the part of the alimentary canal belonging in one somite 

 may be carried back into another. Cross sections from this 

 region are sometimes puzzling on account of this. Posteriorly 

 the dissepiments grow thinner and more transparent from loss 

 of their muscular character, and in the greater part of the body 

 are reduced to delicate films. The aperture in each septum 

 beneath the alimentary canal is circular in outline, and reaches 

 from the ventral side of the canal to the body-wall. Through 

 these apertures pass the ventral blood vessel and the ventral 

 chain of nerve ganglia. 



The Alimentary Canal. 



The pharynx extends from the mouth to about the begin- 

 ning of the fourth somite. It is of the usual character, con- 

 sisting of a thin-walled sac with numerous bands of muscle 

 extending from its outer surface backwards and outwards to 

 the body-wall. When it is empty, its walls are extensively 

 infolded, producing an irregular longitudinal plication of its 

 inner surface. 



At the posterior end of the pharynx, the dorsal wall of the 

 canal presents a narrow transverse inward fold. Behind the 

 fold the caliber abruptly increases again with no change in the 



