276 H. J. VAN CLEAVE 



The walls forming the vas deferens have two nuclei just ven- 

 tral to the cement gland. These nuclei have a diameter of 0.007 

 mm., and each contains a single chromatin mass 0.003 mm. in 

 diameter. A slight ventral dilation of the vas deferens in that 

 part of its course just opposite the posterior edge of the cement 

 gland where it enters the sperm reservoir, is supplied with two 

 small nuclei. These are bilateral in arrangement. Each has a 

 long axis of 0.005 mm., and a short axis of 0.003 mm. 



The muscular sac posterior to the reservoir of the cement gland 

 contains two star-shaped nuclei which lie close to the anterior 

 end of this structure. These have the appearance of lying in a 

 very loose mass of tissue, sending out small projections to the 

 more solid surrounding portions of the sac wall. The muscular 

 wall of this sac contains a small pair of nuclei on its dorsal surface 

 near the posterior end. These are of the type of small oval nuclei 

 found in the body musculature of this genus. Figm*e 17, ms, 

 shows the relations of this structure as presented in a reconstruc- 

 tion from sagittal sections. Very similar conditions have been 

 found in the other species of Eorhynchus but the study has not 

 been carried out in detail. Figure 25 indicates the appearance 

 of the pair of nuclei within the muscular sac of Eo. longirostris. 



The inturned portion of the posterior region of the male, extend- 

 ing from the exterior to the cirrus, is curiously modified in the re- 

 gion nearest the genital opening .when the copulatory apparatus 

 is retracted. At this place there are formed a series of five closely 

 fitted wedge-shaped structures, each of which bears three nuclei, 

 as shown in figure 18, which is a reconstruction drawing from 

 serial sagittal sections. The same condition has been demon- 

 strated in well cleared toto mounts of this species. Connecting 

 this structure surrounding the genital orifice with the arms of 

 the copulatory bursa there is an extremely irregular, inconstant 

 portion , the walls of which vary so in appearance with the various 

 states of retraction or of protrusion of the genital apparatus that 

 the writer has not been able to estabhsh a definite number or 

 arrangement of the nuclei contained in it (fig. 18). 



