NO. 1/ POLYCLAD WORMS HYMAN 5 



linear arrangement along the principal nerve trunks (fig. 10). Of the 

 cerebral eyes, there are two large ones close to the cerebral mass of 

 granules characteristic of many Acotylea, and some large ones in a 

 row along the bases of the main anterolateral nerve trunks (fig. 10). 

 The smaller eyes are peripheral to the large ones, radiating along the 

 nerve trunks. Small specimen (fig. n) has same number and arrange- 

 ment of large eyes as the larger specimen, but the smaller eyes have 

 not yet appeared. Pharynx relatively small with small lateral folds. 

 Sexual region of larger worm removed and sectioned. Conclusion 

 from study of whole animal that sexual maturity had not quite been 

 attained confirmed by study of sections, but essential parts appear to 

 be present. Sexual apparatus close behind pharynx, far removed 

 from posterior end of body. Sexual pores some distance apart 

 ( fig. 9). Male copulatory apparatus (fig. 12) typical of the genus, i. e., 

 the male canal is not definitely divisible into seminal vesicle and pros- 

 tatic vesicle, and may be considered to consist entirely of the seminal 

 vesicle. Vasa deferentia enter separately the lateral angles of the 

 seminal vesicle ; seminal vesicle then turns dorsally, then bends pos- 

 teriorly and extends as slender tube to penis papilla. Seminal vesicle 

 has narrow lumen and thick muscular wall composed chiefly of circu- 

 lar fibers. Xo prostatic glands seen, probably because of immaturity 

 of the specimen. Penis papilla small, rounded, armed with a short 

 stylet in process of being secreted. Penis papilla lies in short penis 

 pocket which forms a penis sheath where it joins the male antrum. 

 Latter moderately large cavity, of moderate length. Female apparatus 

 (fig. 12) has large genital pore, long muscular vagina bent into an 

 S-shape, receiving cement glands along its course. Following entrance 

 of uteri, female canal continues as a small Lang's vesicle, which may 

 not yet be fully formed. 



Remarks. — In an article on Atlantic coast polyclads (Hyman, 

 1939 b), I have shown that "Prosthiostomum" gracile Girard 1850 1 

 is not a Prosthiostomum at all, but fits into Discoplana Bock 191 3. 

 However, since Girard in 1893 himself removed this species from 

 Prosthiostomum and created for it a new genus Euplana, Discoplana 

 must become a synonym of Euplana. The copulatory apparatus of 



1 In a recent publication Pearse (1938) has grossly misidentified Euplana 

 gracilis (Girard) considering it a new species, type of a new genus, Conjuguterus. 

 Conjuguteriis becomes a synonym of Euplana and C. parvus a synonym of 

 Euplana gracilis. Pearse's account of the male system of this species is also 

 erroneous. These corrections are based on an examination of the type speci- 

 men of C. parii<s and a number of other specimens labelled by Pearse with 

 this name. 



