NO. 1/ POLYCLAD WORMS HYMAN 3 



sagittal serial sections. Male and female pores considerably sepa- 

 rated, forming large oval openings. Crescentic seminal vesicle im- 

 mediately behind posterior end of pharynx has very thin wall of 

 muscle fibers paralleling its external contour. Seminal vesicle opens 

 directly into large spherical chambered prostatic vesicle without the 

 intervention of a duct ; ejaculatory duct projects only a short dis- 

 tance into prostatic vesicle (fig. 6). Small penis papilla at beginning 

 of male canal leading away from prostate vesicle. This canal, similar 

 to penis pocket of other Notoplanas, is remarkably long and slender ; 

 runs backward above excessively muscular mass surrounding the 

 male antrum and opens into posterodorsal angle of this antrum. Male 

 antrum large with long anterior extension and lined by a tall epithelium 

 filled with granules of glandular nature ; male antrum surrounded by 

 thick powerful muscle fibers running mostly lengthwise filling all 

 space between antrum, prostate vesicle, and penis pocket. Posterior 

 wall of antrum also muscular. Antrum opens below by large oval 

 male genital pore. 



Large oval female pore considerably behind male pore (relative 

 positions shown in fig. 4). Pore opens into wide funnellike female 

 antrum (fig. 7) with very folded walls; this appearance may be due 

 to the straightening of the specimen. Tall lining epithelium of female 

 antrum has glandular appearance. Vagina proceeds anteriorly from 

 female antrum, makes sharp posterior bend, and some distance be- 

 yond the bend receives the uteri. Beyond uteri long slender stalk of 

 Lang's vesicle runs backward and downward and opens into elongated 

 oval Lang's vesicle. Vagina and stalk lined by ciliated epithelium, 

 outside of which is a fibrous coat which does not appear to be muscu- 

 lar. Numerous cement glands open into vagina and beginning of 

 vesicle stalk. Lang's vesicle lined by very tall epithelium, the distal 

 two-thirds of which is filled with eosinophilous spherules (fig. 8). 

 These suggest an eosinophilous secretion, but it is more probable that 

 they are digesting material. Lang's vesicle probably serves to digest 

 excess sex cells as well as for a seminal receptacle. 



Remarks. — This species undeniably bears a very great resemblance 

 in size, shape, and the details of the copulatory apparatus to Noto plana 

 binoculata (Verrill) 1901 (syn. Noto plana bahamensis Bock 191 3) 

 of which Bock has given a good description, supplemented by some 

 remarks in a recent paper of mine (Hyman, 1939). The similarity of 

 N. caribbeana to N. binoculata is not surprising, in view of the prox- 

 imity of Old Providence Island to the Bahamas, and there still re- 

 mains a little doubt in my mind that I am justified in making a dis- 

 tinct species of N. caribbeana. The following differences may be 



