4 BULLETIN OF THE 



almost milky white. The ventral surface is of lighter color than the 

 dorsal, and there are light areas about the ventral apertures. The 

 pigment is densest in the dorsal median line, where it forms a dark 

 band ; it diminishes toward the sides of the animal, the edges of which 

 are quite destitute of it. The distribution of the pigment in the head 

 region presents many variations. In most cases the posterior borders 

 of the auriculate appendages show two light spots, and there is a 

 third one, somewhat triangular in shape, at the anterior end in the 

 middle line. The marginal area of the head, like that of the body, is 

 free from pigment. Sometimes the whole head region is light with the 

 exception of the middle line between the eye spots, where there is an 

 extension of the dark median band previously referred to. Light non- 

 pigmented areas occur wherever there has been a reparation of the 

 tissues resulting from injury. 



By an examination of the animal in the natural condition, only a few 

 of the internal structures can be identified, because of the large amount 

 of pigment present. When viewed from above, the most striking feature 

 is a large oblong light region, the pharyngeal cavity with its contained 

 pharynges. Immediately behind this a similar but smaller spot marks- 

 the position of the penis. From the ventral side the nervous system 

 may be dimly seen as two long whitish bands united by transverse 

 commissures and coming together in the head region in a bilobed en- 

 largement, the brain. Leidy apparently confused these structures with 

 the excretory organs, no trace of which can be seen on the living animal. 

 He says ('48, p. 250) : " There appears to be nothing peculiar about 

 the arrangement of the blood-vessels, if such they be : the term being 

 applied to two semi-transparent lines passing along each side of the 

 ventral surface, and a third along the middle of the dorsal surface, the 

 three freely communicating with each other by transverse lines and 

 numerous smaller branches, the whole forming an extensive reticulation 

 upon the surface of the body. At the anterior part of each ventral line, 

 I distinctly observed a dilatation to exist." And again : " I could detect 

 no traces of a nervous system." The two '• semi-transparent lines " are 

 without doubt the longitudinal nerve trunks, and the " dilatations at 

 the anterior part of each," the lateral enlargements of the brain. What 

 he means by the " third " line " along the dorsal surface," I cannot say. 

 When sexually mature individuals are subjected to pressure, parts of 

 the vasa deferentia and oviducts can also be made out. 



Phagocata differs from all other Triclads in possessing many pharyn- 

 geal tubes instead of one. All the pharynges lie in a common chamber. 



