196 AQUATIC MICROSCOPY FOR BEGINNERS. 



however, if he refers to them all as Turbellarians, or 

 Turbellaridn worms. The subject has not been stud-' 

 ied extensively by American naturalists, and there is, 

 consequently, nothing in the language to which the be- 

 ginner can be referred for hel[). 



The worms are often visible to the naked eye as 

 minute whitish or flesh-colored floating bodies, or like 

 small bits of white thread in appearance. There are 

 two forms frequently met with which are huge when 

 compared with most of these ciliated creatures, need- 

 ing no microscope to identify them. Both are found 

 on the lower surfaces of submerged stones or sticks, 

 or gliding over the sides of the collecting-bottle. 



The body of one of these common Turbellarians 

 maybe about half an inch in length and nearly five times 

 as long, as broad. It is opaque and almost black. Near 

 the anterior border are two black eyes, which are made 

 conspicuous by the presence of an oblong white space 

 in front of each. The mouth is near the center of 

 the body, and opens on the lower or ventral surface. 

 The worm glides smoothly and rather rapidly over a 

 submerged surface. Naturalists have named it 

 Plandria tdrva. 



The second one referred to somewhat resembles 

 Plandria tdrva, but is usually smaller, and has the an- 

 terior or the head end more nearly triangular. It is 

 similar in its movements and in the presence of two 

 black eyes near the front border, each at the inner 

 margin of a white space, thus giving the worm a cross- 

 eyed appearance. The body is nearly white, and has 

 a dark line passing lengthwise through the center and 

 giving off on both sides many short branches which 

 are themselves often branched, these dark lines on the 



