504 W. JR. Coe — Anatomy of Cerehratulus lacteus. 



dation and modification of two or more simple, epithelial cells. 

 Each of the four cells between them bears a similar, but smaller, 

 process and contains a single nucleus. 



Bounding the opposite two-thirds of the lumen, and separated from 

 the lateral cells by a considerable space, are the less highly modified 

 "median" cells (fig. 2, rac). These cells (fig. 3) are provided with 

 long cilia reaching to the center of the lumen. A dark band is seen 

 just above the bases of the cilia, which results from a thickening of 

 each cilium in this part. The nuclei of the cells are far removed from 

 the lumen. 



A large bundle of nerves (figs. 1, 2,/b') from the dorsal brain-lobe 

 ramifies among the bases of the cells. Surrounding this nervous core, 

 which is really a direct continuation of the core of the dorsal brain- 

 lobe, is a thick mass of nerve-cells [gc) not unlike those of the first 

 type found in the dorsal brain-lobes, with which, in fact, they form 

 a continuous sheet. 



Towards its posterior end the canal [cc') loses its conspicuous lin- 

 ing of elongated sensory cells and ends blindly among the masses of 

 large gland-cells which make up the greater part of the posterior 

 third of the side organ. These large, oval gland-cells (g) are filled 

 with a granular secretion which stains so deeply as to obscure the 

 finer details of the cells. Another mass of gland-cells occupies 

 the anterior border of the side-organ, and the two glandular masses 

 are connected by a thin superficial layer of similar gland-cells. These 

 glands discharge their secretion into the ciliated canal, probably in 

 the space between the median and lateral cells, or amongst the latter. 



The Reproductive Organs. 



The sexes, as in most Neraerteans, are separate and, in the breeding 

 season, can be readily distinguished by their colors. Instead of the 

 white or pinkish color characteristic of this species in the summer and 

 early fall months, as the generative products develop at the approach 

 of winter both sexes take on a decidedly reddish color. In Feb- 

 ruary the males become bright red, while the females are dull 

 red in color ; in some cases appearing almost chocolate-colored. 

 These deep colors are confined mostly to the intestinal region where 

 the generative products are developed. The genital products are 

 fully matured in March and April, although living spermatozoa may 

 be found as early as November. The breeding season extends over 

 a considerable period of time, some individuals depositing their 

 products fully a month before others ; nor are all the products in a 



