494 Howard Edwin Enders. 



animal, occurs a layer of mucus ( ?) that is stained in the sections. 

 I shall have occasion to refer to this structure in the chapter on 

 Habits and Physiology. The esophagus, or a continuation of it, 

 extends through the middle portion of the segment, i. e., the portion 

 bearing the large aliform notopodia, as a convoluted tube of dimin- 

 ished calibre. Directly back of the aliform notopodia it lies for a 

 few millimeters in the median plane of the animal, and its posterior 

 end extends as an invagination into the hirge, dilated green portion 

 of the intestine with which it is continuous. Sections through this 

 region show two concentric layers of epithelium: an inner layer of 

 ciliated cells and an outer layer of cells filled with green granules. 



The conspicuous dilated green portion of the intestine is confined 

 to the thirteenth segment. Its anterior half consists of a thin-walled 

 dilated sac, but it becomes constricted where it passes beneath the 

 accessory feeding organ of the thirteenth segment. In the posterior 

 half of the segment it again becomes dilated. This darker portion 

 forms two and one-half convolutions in a horizontal plane before it 

 reaches the fourteenth segment (the first palette). In the palette 

 the intestine has a smaller calibre but it is still seen by transparency 

 as a dark green tube. In the intervals between the palettes it is con- 

 siderably constricted, but it again becomes dilated within each palette 

 where it makes a siphonal curve in a dorso-ventral plane and then 

 passes into the posterior region of the annelid. In the posterior 

 region it is less green in color. When the animal is extended the 

 intestine appears as a slightly sinuous tube of gradually diminishing 

 calibre. Its constriction and dilatations correspond wdth the septa 

 and segments it traverses. It opens to the exterior by the large 

 gaping anus located dorsally at the posterior end of the animal. 



Claparede described the pigmentation of the epithelium of this 

 middle region of the body in his AnneUdes sedentaires (1873). Its 

 distribution has since been correctly described by Joyeux-Laifuie 

 ('90) and by Kay Lankester (Benham's observations, '97). It is 

 distributed in the epithelial cells of the intestine in the form of 

 spherical granules of varying size. They are embedded in the proto- 

 plasm of some of the cells in such nmnbers as to give the cells an 

 irregularly distributed green color, as seen in section, with moder- 



