lander: anatomy of hemiurus crenatus. 23 



0.198 mm. long and 0.112 mm. wide. Each consists of a compact mass 

 of cells of various sizes, the largest being about 14.5/x in diameter, and 

 the average being about 7.2/x, in diameter. The cells being closely 

 packed are polyhedral, and all except the very smallest are practically 

 filled with yolk granules. Near the centre of each cell is to be seen a 

 spherical or slightly oval deeply staining nucleus. In the position of 

 the glands adjacent to the opening into the ducts the cell boundaries are 

 indistinct, and the paired vitelline ducts are often filled with free yolk 

 granules. 



One of the paired vitelline duels arises from the ventral surface of 

 each vitellarium near its mesial border and a little nearer its anterior 

 than its posterior end. Each duct widens out somewhat where it joins 

 the vitellarium, its wall being continuous with that of the gland. The 

 two vitelline ducts take a direction ventral and medial, meeting directly 

 above the shell-gland, where they unite to form the narrow unpaired duct 

 which traverses the shell-gland to reach the ootype, with which, as before 

 stated, it unites. 



The sexual duct, upon emerging from the shell-gland, is called the 

 uterus ; it turns posteriad, forms two or three short transverse loops, and 

 then a few which are more nearly longitudinal ; some of these may ex- 

 tend to the posterior end of the trunk or even a short distance into the 

 appendix. From this region it passes forward (Fig. 1), forming a com- 

 plicated series of loops and coils, which usually occupy the greater por- 

 tion of the body between the ovarium and the testes, and lie both dorsal 

 and ventral to the intestinal coeca. In passing forward it sometimes makes 

 a few loops dorsal to the testes, and then proceeding over the ventral sucker, 

 joins the ejaculatory duct to form the genital sinus. The terminal portion 

 of the uterus (Plate 3, Fig. 28) lies posterior and ventral to the semi- 

 nal vesicle and ejaculatory duct. There is no great variation in the 

 diameter of the uterus, though the portions near the shell-gland and 

 genital sinus are smaller than the intervening portion, which is usually 

 more or less distended with eggs. The transverse loops of the uterus 

 ventral and posterior to the vitellaria are very often filled with sper- 

 matozoa the movements of which render the identification of this part 

 very easy in living worms. This portion of the uterus has been desig- 

 nated by Looss ('94) as the receptaculum seminis uterinum. According to 

 Looss the spermatozoa, which have reached this place by passing through 

 the entire length of the uterus, are retained here for use as needed in the fer- 

 tilization of eggs in the ootype ; many of them, however, pass on through 

 the ootype into the seminal receptacle, whence they are prevented from 



