5© BULLETIN OF THE LABORATORIES 



make it reasonably sure that our species is really D. tigris. It is 

 quite variable in size and form. The cylindrical body is strongly 

 curved ventrally. The head is distinctly set off from the body by a 

 suture as represented by Eyferth but not by Eckstein. The sides of 

 the neck extend into a sharp spine on either side, which, however, may 

 be easily overlooked. There is a sensory cylinder which forms a third 

 prominence upon the front. The foot consists of but a single evident 

 segment which is quite short. The appendages assume a variety of 

 appearances. Usually they seem to form a flattened triangular plate 

 curved in the same plane as the body. This appearance is figured by 

 Eckstein, though he describes the appendages as consisting of two pairs, 

 the outer half as long as the inner, both being united at the tips into 

 one plate. Eyferth says, on the other hand, that the foot bears two 

 unequal, bristle-like, curved claws, but his drawing shows two equal 

 claws. Our experience confirms Eyferth' s account. Like RattuliAs^ 

 this species moves in circles or arcs of circles when lashing its tail, but 

 has the power of moving in a straight line by the use of the cilia alone. 

 The maxtax is nearly as drawn by Eckstein. The chief organs are 

 two anchor -like indurated processes which are unlike in length and 

 form. The walls of the maxtax are furnished with ring-muscles. 

 The stomach is glandular and its cells contain large globules of fatty 

 matter. The intestine is pear-shaped and furnished with numer- 

 ous cilia. The contracting vessel is large but the lateral vessels 

 are not easily seen and I can add no details. The single cervical eye 

 is large and seated on a large elongate ganglion. The ovary is small 

 and the egg, when present, occupies the left side of the body on its 

 ventral aspect. The total length is about .20 mm. of which the body 

 forms .16 mm. The longer claw measures, in large specimens, .048 

 mm. and the shorter only .036 mm. Sometimes I fancied that I saw 

 two .lateral spines as described by Eckstein. The width of the lorica 

 is about .65 mm. This species was encountered in Ohio and Minne- 

 sota in all situations and seasons. 



DiURELLA INSIGNIS, Sp. 11. 



{Plate IV. Fig. 6.) 



A larger species than the above is found in Minnesota. The 



length, exclusive of the claws, is from .17 to .20 mm. The claws 



are .06 mm. long, one being much longer than the other. There are 



spines in the cervical region similar to those described in in the above, 



