ZOOL— Vol. III.] HEATH— EPIDELLA SQUAMULA. 121 



surface somewhat to the right of the median line. Here it 

 makes its exit, and after one or two slight bends unites with 

 the yolk-duct, and passes on to the ootype or egg-mould (fig. 

 13, ^). During the reproductive period the ripe eggs pass 

 from the ovary and take up their position within this first 

 section of the duct, which accordingly becomes much dis- 

 tended, and closely united with its sheath. The free por- 

 tion, outside of the ovary, remains unchanged, and serves 

 to convey the eggs one by one into the egg-mould. 



The yolk-glands (fig. 11) are scattered widely over the 

 body, occupying all the available space between the 

 branches of the alimentary canal, excretory system, and 

 the various organs of the reproductive system. In each 

 follicle are cells in all stages of the yolk-secreting process ; 

 at first containing relatively few refractive granules imbed- 

 ded in the cytoplasm, but in the latter stages becoming 

 metamorphosed into a mass of yolk-granules, among which 

 one may still see the nucleus. The ducts leading from the 

 follicles on either side of the median line finally unite to 

 form one great transverse canal situated immediately in 

 front of the ovary. On the left side this becomes distended 

 into a yolk reservoir, from which a relatively slender tube 

 arises from about the center of its dorsal, or at times pos- 

 terior, surface, and coursing toward the right unites with 

 the oviduct, and further on enters the midst of the seminal 

 receptacles (fig.i3,s.r.). The latter consist of delicate, thin- 

 walled vesicles, usually seven in number, grouped about 

 and opening into the oviduct. From this point this last 

 named canal passes forward, and enters the egg-mould or 

 ootype of van Beneden. In close proximity to the point of 

 union of the two are a large number of unicellular glands, 

 the shell glands, whose general position and appearance is 

 represented in fig. 13, s. g. 



The ootype is elliptical or pear-shaped in form, with the 

 pointed end directed toward the exterior. Its walls are rel- 

 atively thick, and are composed of masses of cells arranged 

 in the form of three pads, as shown in fig. 13, o. Each 

 consists of finely granular protoplasm, and contains several 

 distinct nuclei, but no farther indication of a number of 



