l6o ESTHER F. BYRNES. 



occurs in the armature of the third joint of the large ramus of 

 the maxillipeds of the fourteen -jointed and seventeen-jointed 

 forms. The armature usually consists of three large hairs and 

 two very small ones growing close together at the base of one of 

 the large hairs (Fig i, E\ In the fourteen-jointed forms, these 

 two small hairs are strikingly shorter than they are in the seven- 

 teen-jointed form. With this single exception, the maxillipeds 

 are precisely alike in both groups. 



I am aware that Herrick describes the armature of the terminal 

 segment of the larger branch of the maxilliped of C. parcus, as 

 consisting of four hairs. I have found an instance in which four 

 large hairs of almost uniform size occur, but a more frequent 

 condition in the Long Island Cyclops is seen in those instances 

 which show three large hairs and two short ones, in place of the 

 four hairs of Herrick (Fig. I, R}. 



Among the many Cyclops I have studied, I have seen but one 

 with eighteen segments in the antennae. In this case the eigh- 

 teenth segment is derived from the seventh segment, by transverse 

 division, at the level of the seta. In both right and left antennae 

 the division is incomplete, extending but half way across the 

 segment. 



I have studied this Cyclops with great care, and in every 

 detail of structure, it agrees perfectly with the forms associated 

 with it in showing the chief species-characteristics of C. parcns. 



I have repeatedly made written records of body-segments and 

 appendages showing the complete armatures, and have made 

 many outline drawings of those parts that are correlated in the 

 determination of species, and I believe no room for doubt remains 

 that the Cyclops with thirteen and with fourteen antennal seg- 

 ments, as well as the form with eighteen segments, are all to be 

 referred to the type with seventeen segments in the antennae. 

 Those having thirteen and fourteen segments, known as C. 

 insignis, though very abundant forms and though sexually mature, 

 do not represent a group of sufficient permanency to warrant 

 us in regarding them as representatives of a distinct species. 

 They are rather to be considered as transitory stages which, 

 though capable of producing young, have not as yet attained 

 their maximum growth, or their highest degree of complexity. 



