154 ESTHER F. BYRNES. 



small hair at its base. Attached to the immovable dactyl is a 

 small, movable one. 



9. The antennae are about the length of the cephalothorax. 



The points in which the Long Island Cyclops that I have 

 studied differs from C. parcus are : In the number of antennal 

 segments, there being 13 instead of 17, and in the occasional 

 variation in the armature of the outer ramus of the fourth foot, 

 there being but one outer spine and one seta, where C. paints 

 has typically two spines ; as well as in the armature of the ter- 

 minal joint of the large ramus of the maxilliped, where two 

 small hairs replace one large one ; also in the armature of the 

 distal joint of the fifth foot, which carries an outer hair, in place 

 of the unserrated spine which is present in the form with seven- 

 teen joints in the antennae. 



As the correlated characteristics of species occur with great 

 regularity in the Cyclops, and as the form under consideration 

 seemed, both on account of its relatively large size and its fertil- 

 ity, to be a mature form, I searched for similar individuals but 

 for a long time failed to find them. 



In the summer of 1899, I had the opportunity of collecting 

 large numbers of Cyclops at Cold Spring Harbor, L. I., where sev- 

 eral fresh-water ponds afford excellent opportunities for the study 

 of a variety of species. Though I have worked over some of this 

 material with great care, I have never met with a single instance 

 of a thirteen-jointed antenna. 



In March of the present year, 1903, I again met with a num- 

 ber of Cyclops having thirteen-jointed antennae. This material 

 was collected in one of the large, shallow, fresh-water ponds at 

 Jamaica, Long Island. The copepods were found in great num- 

 bers hidden beneath the fallen leaves along the edges of the 

 pond. Again I noticed marked color-changes incident to the 

 development and laying of ova. Some were red in the body and 

 carried blue eggs in their paired sacs, while many were dark in 

 color and carried about the partly developed reddish embryos. 



Associated with these larger forms were smaller Cyclops, often 

 without eggs, and emerald green to the naked eye, owing to the 

 numbers of green protozoa that had attached themselves to the 

 cuticle and almost concealed the host. The larger Cyclops with 



