512 A. E. Verrill — Marine Planarianfi of New England. 



integument. The caudal cirri are often lost by injuries, but are 

 quickly reproduced. 



The otocyst is small, circular, situated well forward at about the 

 anterior fourth; otolith cup-shaped. In some specimens the otocyst 

 appears to be rudimentary or wanting ; in many it can scarcely be 

 seen while living, owing to its small size and the great amount of 

 pigment in the integument; in others it is easily visible. 



Mouth central or subcentral, simple, circular or transversely ellip- 

 tical, highly dilatable, surrounded b^^ circular muscular fibers. The 

 digestive cavity is capacious, more or less irregular in outline. It is 

 usually filled with various Entomostraca and other small crustaceans. 



The genital openings are small, round, near together, and usually 

 not very distinct. The male orifice is a little in advance of the base 

 of the median caudal cirrus. The penis, as seen from beneath and 

 foreshortened in mounted specimens, is usually ovoid or conical; 

 when protruded it is rather elongated, cylindrical or tapered, often 

 curved, with a conical tip. Its base is surrounded by a circular 

 seminal vesicle (pi. xliv, figs. 6-10, /■) which receives the vasa def- 

 erentia (d) on the right and left sides. The latter are voluminous, 

 more or less saccular and contorted posteriorly, when filled with 

 their contents. 



The spermarian folicles (t) are small, numerous, pyriform, and 

 extend along each side above and partly external to the ovaries and 

 oviducts, as far as the anterior margin of the digestive cavity, 

 where they converge and nearly or quite blend at the median line, 

 when fully developed. 



The oviducts are large and saccular and lie close to the digestive 

 cavity, on each side; posteriorly they are often much swollen by 

 large clusters of relatively large mature ova, of which there are 

 often six to ten, arranged in two or three rows, in each cluster; 

 those farthest back often crowd against and more or less distort 

 and conceal the spermatheca and other organs, and make that part 

 of the body gibbous externally. 



The spermatheca (figs. 6, 7, 8, s) is large, glandular and saccular 

 dorsally, variable in shape, but when least crowded it is generally 

 broad-cordate or reniform ; the emargination of the posterior side 

 includes the female orifice and vagina. Its ventral surface is 

 covered with small brownish, chitinous, conical outlet-tubes or 

 " mouth-pieces," differing in size and varying in number in differ- 

 ent specimens from six or eight up to thirty or forty; most fre- 

 quently twelve to fifteen fully developed ones and several smaller 



