274 H. J. VAN CLEAVE 



shaped nuclei whose arrangement is shown in figure 16. The ven- 

 tral retractor of this same species is similarly furnished with two 

 nuclei. These are of the same type as those already described 

 for the dorsal retractor. In no case was any evidence discov- 

 ered indicating the presence of other nuclei of any type in these 

 structures. 



Eorhynchus longirostris. In members of this species the 

 arrangement of the proboscis receptacle retractors is identical 

 with that just set forth for Eo. gracilisentis. The nuclei are of the 

 same number, the same appearance, and have identical relations 

 within the retractors. Figure 28 shows the nuclei of the dorsal 

 retractor of the proboscis receptacle. 



Eorhynchus emydis (Leidy), Eorhynchus cylindratus, and Eo- 

 rhynchus tenellus show the identical condition of the retractors 

 of the receptacle as described for the other species of the genus. 



8. Cement gland 



In members of the genus Eorhynchus the cement gland pre- 

 sents a condition at wide variance from the type most commonly 

 found in the other genera of Acanthocephala. Instead of consist- 

 ing of a series of independent sac-like glands in the posterior 

 region of the male, as in many genera, the cement gland is a 

 compact mass. Bieler ('13) has suggested that this deviation in 

 structure, together with the fact that a single covering encases the 

 mass, is of value in differentiating the Eorhynchi from their near 

 relatives. This characteristic was not mentioned by Hamann in 

 his definition of the genus. In all of the species examined the 

 nuclei of the cement gland are oval with a compact central 

 chromatin mass. 



Eorhynchus gracihsentis. In this species eight large oval nu- 

 clei lie imbedded in the mass of the gland (fig. 9, eg.) These are 

 the only nuclei present in the entire structure. The study of 

 toto mounts and of sagittal sections demonstrated that, though 

 these nuclei are uniformly distributed through the gland, there 

 is an evident arrangement in two lateral groups each of four 

 nuclei. 



