No. i.] DINOPHILUS GARDINERI. 17 



pletely ciliated, and, in addition, each segment shows laterally two 

 tufts of long cilia and a strong bristle anteriorly placed. These 

 probably indicate the presence of two rings of cilia on each 

 segment. The head bears two tufts of long cilia in front, and 

 the tail bears several bristles. These are probably of a sensory 

 nature. 



No sexual dimorphism is present ; it is impossible to dis- 

 tinguish the sex of young individuals. In mature females the 

 paired ovaries are strongly colored and may be clearly seen. 



This species differs from D. gyrociliatns (apatris) and D. 

 nictauicroidcs in its lack of sexual dimorphism ; in the number 

 of segments and in the arrangement of cilia it differs from 



o o 



D. gigas (7 segments), D. tacniatns (5 segments), D. pygniacns 

 (5 segments), and D. simplex (4 segments) ; in the arrangement 

 of cilia and in the possession of an unsegmented tail it differs 

 from D. vorticoidcs (caudatns}. 



The bilobed or crescentic shape of the eyes of Dinophilus 

 often looks as if they were on the way to becoming double, as 

 is the case with some Turbellaria. I have found two specimens 

 in which the right eye was made up of two spheres completely 

 separated from each other. In one case they lay close together ; 

 in the other, one sphere was in the normal position, the other 

 in the next segment (Fig. 2). 



In explanation of the disappearance of Dinophilus, alluded to 

 above, I have to offer an observation of a stage in its life 

 history which to my knowledge has not been noted before. On 

 June 27, 1899, in my search for specimens I came across cap- 

 sules imbedded in the tangle of algae. Through the thin trans- 

 parent walls I could distinctly see the characteristic form, color, 

 and eyes of DinopJdlns. In addition to the capsules, eight 

 specimens were found on the same day. These were put by 

 themselves in a shallow glass dish containing salt water and 

 some algae, and were watered from day to day. At the end 

 of a week only five specimens were seen ; on searching for 

 the other three, three capsules were found. I then realized 

 that these capsules really represented an encysted stage of 

 DinopJiilus. The five remaining specimens were transferred 

 to a fresh dish of clear water. Four of them disintegrated ; 



