CELL CONSTANCY IN THE GENUS EOEHYNCHUS 275 



Eorhynchus longirostris. The gland in this species stands in 

 marked contrast to the type preceding. While the nuclei are 

 clearly of the same character as those of Eo. gracilisentis their 

 number is just doubled. Instead of the eight large oval nuclei 

 there are sixteen of the same general character (fig. 20, eg) . 



Eorhynchus emydis. This species contains a long cylindrical 

 cement gland bearing eight nuclei. The size of the gland is indi- 

 cative of the degree of maturity of the individual. Figure 42 

 shows this gland in an immature male. The eight nuclei within 

 thts small mass are arranged in two distinct groups. The same 

 gland in a fully matured worm not only has increased considerably 

 in size (fig. 41) but at the same time has undergone a complete 

 rearrangement of the component nuclei, resulting in a single line 

 of nuclei running the length of the gland. 



Eorhynchus cylindratus and Eorhynchus tenellus both have 

 cement glands of the type just described. In each case the eight 

 large nuclei occur in an elongated cylindrical organ. The arrange- 

 ment of the nuclei in each of these species is the same as that 

 described for Eo. emydis. 



9. The male genital apparatus 



Eorhynchus gracilisentis. The cirrus in this form is supplied 

 with nuclei of two types, and in some instances a clear distinc- 

 tion could be drawn between the two kinds of tissues connected 

 with the respective types of nuclei. The portion of the cirrus 

 lying nearest to the sperm duct has a pair of large lateral rmclei 

 in the dorsal region (fig. 18, ci) in which the chromatin has a 

 strikingly characteristic arrangement in small masses scattered 

 through the nucleus, with a tendency toward collecting on the 

 nuclear wall. These spheroidal nuclei are 0.007 mm. in diameter. 

 Slightly anterior to this pair of nuclei and in the region of the cir- 

 rus farthest removed from the duct are two slightly larger spher- 

 ical nuclei (fig. 18, ci) measuring about 0.009 mm. In these, 

 the chromatin tends toward the formation of closely compacted 

 masses lying in the center of the nuclei. 



