COLD SPRING HARBOR MONOGRAPHS. 



VII. 



was also collected along the borders of a shallow pond fed by the 

 cold water from a woodland brook, and overgrown with water 

 weeds along its banks. 



This Cyclops was very deeply pigmented, especially on the 

 cephalo-thorax, the posterior thoracic segments, the outer margins 

 of the abdomen and the stylets. The outer rami of the swimming 

 feet were deeply and uniformly pigmented. The inner rami of the 

 fourth feet were quite colorless. This is the appendage to which 

 the male attaches itself during copulation. The ovaries and the 

 embryos of this Cyclops were almost colorless. 



The second form of ater was taken from an unshaded pond 

 where the shallow water became uniformly heated, and where the 

 temperature was considerably higher than in the pools mentioned 

 above. The Cyclops from this locality contained much less pigment 

 and appeared banded, having dark lines across the thorax. The 

 appearance of this form was made very striking by the bright 

 orange color of the ovaries. 



All the forms of ater agreed in the number of antennal seg- 

 ments, in the armature of the swimming feet and in the fifth foot, 

 as well as in the general proportions of the body. 



The number of hairs on the seventeen antennal segments of C. 

 ater, counting from the base is as follows: 8, 4, 2, 6. 4. 2, 2, i, i, 

 o, I, 2, o, I, 2, 3, 8. 



The armature of the terminal segments of the swimming feet 

 is as follows : 



Foot No. 



Ramus, Outer or Inner. 



Outer Spines 

 Apical Spines 

 Apical Seta . . 

 Inner Setse . . 



sa-seta in place of spine. 



The setae are long and strongh- developed and the spines are 

 stout and distinctly serrated. 



The fifth feet of ater are one-jointed and bear a well formed 

 median spine, not always serrated and two long, slender setae, 



