8 PROCEEDINGS OF THE ACADEMY OF [Feb., 



only slightly coiled, entering the anterior enlargement of the lumen of 

 the penis nearly at right angles. Penis short and broad, nearly filling 

 the atrium (similar to that of P. maculata). Uterus large, dorsal, ex- 

 tending forward nearly to the pharynx chamber; stalk of the uterus 

 passing to the left side, dorsal to the vasa deferentia and oviducts, 

 and entering the atrium laterally and ventral to the entrance of the 

 common oviduct (Plate I, figs. 5 and 6). 



Reproduction by Fission. — Like Planaria maculata, this species 

 reproduces both sexually and asexually. Indications that fission had 

 occurred were observed in May, 1901-1905. In May, 1905, while all 

 the individuals in one branch of a certain stream were sexually mature 

 and depositing egg-capsules, those in another branch of the same 

 stream were found in all stages of fission and regeneration (Plate I, 

 figs. 7-10). During the last week of May and first week of June a few 

 individuals showed regenerating atrial organs. The same difference, 

 as to sexual matiu-ity and fission, was observed in collections from the 

 two branches of the stream in October, and at the date of writing 

 (February 7th) there are no sexually mature worms among the thirty 

 to forty specimens which were reproducing by fission when brought 

 into the laboratory in October. About half of the number have 

 divided in the aquarium. Fission occurs at a point nearer the pharynx 

 than in P. maculata (fig. 7), 



Regeneration. — Both anterior and posterior regeneration at all levels 

 proceeds much as in P. simplicissima, but both regeneration and form 

 regulation are more rapid. 



Habitat. — Planaria morgani is found on the under side of stones and 

 dead leaves in a small stream, one branch of which flows through the 

 Bryn Mawr College campus. The authors have not found it elsewhere. 



Explanation of Plate I. 



Fig. 1. Freehand sketch of living planarian, magnified five times. Atrial 

 organs present (a). Limits of the digestive tract indicated by dotted out- 

 line. 



Fig. 2. Same of an individual without atrial organs. 



Fig. 3. Camera drawing of whole mount, showing pharynx and branches of the 

 digestive tract. Magnification 10 diameters. 



Fig. 4. Reconstruction from camera drawings of frontal sections, sho^ving 

 cerebral gangUa, lateral nerve cords, cephalic nerves, eyes, and ovaries. 

 Mag. 35 d. 



Fig. 5. Reconstruction of reproductive system from a series of frontal sections, 

 dorsal aspect. p. =pharynx. /. =testis. od. =oviduct. v.s. =vesicula 

 seminalis. ■u.=uterus. p.Z. = penis lumen, pe. =penis. a. =atrium. c.o. 

 = common oviduct. ?•.= reproductive pore. m.s. =uterus stalk. Mag. 10 d. 



