POLYCLADS OF THE EAST COAST — PEAKSE 93 



There are no marginal eyes at the anterior end for a space of about 

 0.15 mm wide ; on each side of this a group of about 35 eyes extends 

 along the margin, about two-thirds of the eyes being anterior to the 

 brain. The cerebral eyes are usually arranged in the form of a horse- 

 shoe or a V, with the opening directed posteriorly. They lie dorsal 

 to the brain and extend in front of and behind it. 



The enteron consists of a median stem and about 22 lateral branches 

 on each side. The twigs of these extend to near the margin through- 

 out the body. The pharynx is often coiled within its sheath or may 

 even be thrown out of the body in preserved specimens, but in living 

 worms it rests longitudinally and in moving specimens is indicated 

 by a median ridge near the anterior end. In it longitudinal muscles 

 lie within the circular muscles. 



About 300 small rounded testes may be seen interspersed among the 

 lateral twigs of the enteron. They extend forward on either side to 

 just posterior to the brain. The male genital pore lies immediately 

 behind the pharynx. Two vasa deferentia enter the genital bursa 

 near the posterior end from the sides and bend sharply to extend back- 

 ward at right angles along each side of the median stem of the ente- 

 ron. The female genital opening is close behind the male opening 

 about 0.2 to 0.3 mm distant. The uteri coil along the sides and ex- 

 tend almost to the posterior end of the body. The ovaries are diffuse 

 lobate structures on either side of the median enteric stem forward as 

 far as the anterior tliird of the pharynx. The genital organs do not 

 ■occur along the margins of the body ; a zone about 0.3 mm wide is thus 

 left free. 



Color, unpigmented except for the eyes. Living specimens are 

 ■cream color or dirty white, and darker j'^ellowish-brown toward the 

 median line because the internal organs show through the integument. 



Type.—V.S.'NM. no. 20194; from St. Vincent Bar, Apalachicola 

 Bay, Fla. ; collected August 16, 1935, by A. S. Pearse. 



Reinarks. — This species was not uncommon in Apalachicola Bay 

 during 1935-36. It was usually found at the surface of pails of shells 

 that had been brought in from the oyster bars and allowed to stand. 

 Several large specimens were collected in St. Joe Bay, Fla., March 

 24, 25, 1936. Some of them laid eggs in the laboratory. The two larg- 

 est measured 22 by 3 and 24 by 3.3 mm when extended and crawling 

 A young specimen was collected near Crystal River, Fla., on October 3, 

 1935. During the summer of 1938 specimens were collected at Beau- 

 fort, N. C. The species differs from Prosthiostomum gracile Girard, 

 1850, in its larger size and in the arrangement of the eyes. 



