21 
ting’uished, but the details were somewhat unsatisfactory, owing to the 
condition of the material. 
Nervous system. — The brain (figs. 10-11, 15) surrounds the esoph- 
agus at a plane corresponding rather closely to the excretory pore, 
Fig. 13. — Enlarged lateral view of a midgut portion of a worm cleared in glycerine. Compare this 
with fig. 12, and notice the following details: The dark field in the middle is the lateral band 
(enlarged still farther in fig. 14); this shows two parallel halves (dorsal and ventral), separated 
by a middle row of cells; the wavy, more or less parallel lines represent the somatic muscles; 
near the sides of the figure one obtains a lateral view of the large reticulum shown in fig. 12; on 
deep focus, this reticulum is, of course, much more distinct than can be shown in a view draAvn 
in perspective. 
namely, about 416yu from the anterior extremit 3 ^ There is some slight 
variation in the diflerent specimens, so that this measurement is some- 
