158 ESTHER F. BYRNES. 



is relatively greater in the Cyclops with the fourteen-jointed an- 

 tenna than in the adult C. parcus, though in C. parcus the stylets 

 are characteristically long. Another slight difference is seen in 

 the presence of a hair in the form with the fourteen-jointed anten- 

 nse, in place of a small spine on the inner angle of the distal 

 joint of the fifth foot of the seventeen-jointed form. Compare A' , 

 B', C, Fig. i. Moreover, the distal joint of the so-called C. insignis 

 is strikingly long, longer than the corresponding joint in C. parcus. 

 The difference between the two forms seems to be almost entirely 

 one of proportion and size, the insignis-\\V.& form being slightly 

 smaller than C. parcus, and often with fewer or no eggs. 



In favor of the existence of a separate species for those forms 

 with fourteen-jointed antennae, and against the suggestion made 

 by Herrick that C. insignis represents a transitional stage in 

 development, Schmeil urged the occurrence of the Cyclops in 

 large numbers, and its relatively large size, both of which obser- 

 vations I can confirm. I can not, however, agree with Schmeil's 

 interpretation ; although the form is abundant and moderately 

 large, it is often, though not always, without eggs either in the 

 body or attached, when older forms associated with it are re- 

 markably prolific. Moreover, if studied at the right stage, the 

 form with fourteen segments in the antennae gives frequent signs 

 of being still in a period of growth characterized by morphologi- 

 cal changes. The fact that the smaller form is densely covered 

 by foreign growths indicates that it has not very recently moulted. 

 In this connection it may not be irrelevant to allude to a few 

 observations made on isolated copepods. 



I separated a number of Cyclops in a small watch crystal. 

 All were about the same size, some green to the naked eye, 

 some dark, and others carrying eggs. A few days later my 

 attention was drawn to a bright red Cyclops with a perfectly 

 clean cuticle. It had seventeen segments in the antennas, and 

 from the absence of protozoa on its surface it must have moulted 

 quite recently. I then looked about in the dish for cast-off 

 skins and found one still well covered with protozoa and having 

 fourteen-jointed antennas. 1 



1 Inasmuch as there were other individuals in the watch crystal, this is by no 

 means conclusive proof that the seventeen-jointed form had shed the fourteen-jointed 

 skin, but I could find no other explanation of its presence in the dish and I offer the 

 fact for whatever it is worth. 



