243] TURBELLARIA FROM THE MISSISSIPPI BASIN— HIGLEY 49 



March and April, the intestine is more or less obscured by the large yolk 

 glands which extend forward as far as the eyes. These are heavily lobed but 

 when fully developed become compact with a very thin dividing wall. Over- 

 lapping the posterior third on each side is the testis, very finely granular but 

 much lighter in color. The ovary is small, posterior in position and well 

 embedded in the parenchyma. The eggs which have a diameter about one- 

 fourth that of the body, are thin-shelled and gray in color. They pass the 

 embryological stagey in the uterus lying near the middle or a little to one 

 side in close proximity to the genital pore which is very large. As a whole 

 the reproductive system is conspicuous. 



The most noteworthy details of structure may be summarized as: first, 

 a broad head and tail region with a large amount of parenchyma tissue; 

 second, a small pharynx, and third, large yolk-glands. 



Dalyellia megacephala nov. spec. 

 Figures 23, 25 and 39 



The situation in which this species is found is of typical formation, the 

 important details being a muddy bottom, a small amount of algae, and a large 

 animal community. The general appearance is striking, due especially to 

 the relatively large eyes and pointed head. The length is about 0.75 mm. the 

 width 0.2 to 0.25 mm. and the depth somewhat varying but never more than the 

 width. In shape the animal very closely resembles many others of the same 

 general type. The anterior end is bluntly pointed and flat. The middle region 

 of the body is rounded out, being plump and much thicker than the rest. 

 Then the posterior end is shghtly attenuated and more pointed than the head 

 but cylindrical instead of flat. There is really no color but to the naked eye 

 the whiteness is opaque flecked with the black spots of eyes which are large 

 enough to be easily seen. 



The integument is conspicuous, since its boundaries are definite and clear 

 cut. Here again the inner wall is heavy. The cilia are very short and fine, all 

 of about the same size and evenly distributed over the body. The rhabdites 

 are not gathered in special tracts but are scattered thruout the inner portions 

 of the epithelial cells. The arrangement is quite lattice-like in its regularity, 

 the small groups of straight rods lying at right angles to each other. 



The muscular system is heavier than in many forms, as much of the loco- 

 motion is effected by means of body contraction. It lies, however, very near 

 the integument, a condition which is partly due to the fact that the parenchyma 

 is not abundantly developed. The lack of parenchyma seems to be correlated 

 with the relatively large digestive system, which nearly fills the body mass. 

 The pharynx is very large and extends far forward leaving anterior to it only 

 a small triangular area. The wall of the pharynx is made up of two kinds 

 of cells, regularly placed. Those lying longitudinally are very slender and 

 reach the whole length of the organ. Those extending around are also narrow 

 and thread-like, and together with the longitudinal cells make a cross-hatching 



