262 



American form, P. festae Borelli. P. agilis differs from P. macidata as 

 described by Curtis (1902) chiefly in the shape of the penis lumen. 

 The opening is not directed as far downward as in P. maculata and the 

 vase-shaped lumen divides anteriorly to form the two seminal vesicles. 

 Two figures are given to show the atrial organs. The dorsal view (Fig. 3) 

 is from a specimen collected in November. The lateral view (Fig. 4) is 

 a reconstruction from a specimen obtained in April. In two other spe- 

 cimens collected at the latter time, the seminal vesicles and the penis 

 lumen are so swollen and distorted by the spermatozoa present as to 

 measure nearly twice the diameter of the one shown. In all specimens 

 collected in the latter part of May they are empty and reduced to 

 slender tubes. 



P. agilis is very restless and active, in this particular resembling 

 P. doroiocephala Woodworth. I have had but a few specimens of living 

 P. doroiocephala for comparison, but found that they ordinarily came to 

 rest before P. agilis when placed together and subjected to the same 

 kind of stimulus. When in motion the cephalic appendages of P. agilis 

 are usually elevated and active ; the head is frequently turned from side 

 to side or extended upwards in testing reactions, and many changes are 

 made in the direction in which the animal is moving. 



In a recent paper Child speaks of an unnamed Galifornian pla- 

 narian which "differs from P. maculata in color, length of 'auricles' and 

 length of pharynx". The figure given resembles P. agilis except in 

 shape at the tip of the anterior end and in the shape of the circum-ocular 

 areas, the latter a somewhat variable characteristic. It is quite possible 

 that the planarian which Child had before him is the one to which I 

 have given the name P. agilis. I have found no further description of 

 this species. 



Works cited. 



Borelli, A. 1898. Viaggio del Dr. Enrico Festa nell' Ecuador e regioni vicine. 



IX. Planarie d'acqua dolce. Boll. Mus. Zool. Anat. Comp. Torino. Voi. 13. 



No. 322. 

 Child, C. M. 1901. The Habits and Naturai History of Stichostemma. Amer. Nat. 



35. p. 975—1006. 

 1906. The Relation between Regulation and Fission in Planaria. Biol. Bull. 



11. p. 113—123. 

 Curtis, "W. C. 1902. The Life History, the Normal Fission and the Reproductive 



Organs oî Planaria maculata. Proc. Boston Soc. Nat. Hist. 30. p. 515—559. 



PI. 11. 

 Graff, L. von. 1882. Monographie derTurbellarien. 1. Rhabdocoelida. Leipzig. 1882. 

 Kennel, J. 1888. Untersuchungen an neuen Turbellarien. Zool. Jahrb. Anat. 3. 



p. 447—486. PL 2. 

 Ott, H. N. 1892. A Stuiy of Stenostoma leucops 0. Schm. Journ. Morph. 7. 



p. 263-304. 

 Woodworth, W. McM. 1897. Contributions to the Morphology of the Turbellaria. 



IL On some Turbellaria from Illinois. Bull. Mus. Comp. Zool. 31. p. 1 — 16. 



PI. 1. 



