1 68 ESTHER F. BYRNES. 



Four individuals constitute a second group having typically 

 ten antennal segments, two-jointed rami, and tivo-jointed fifth feet. 

 Two of these individuals show marked variation, one in having 

 three-jointed rami in the swimming feet, the other in having a 

 one -jointed fifth foot. 



Four individuals constitute a third group, characterized by 

 eleven-jointed antenna, three-jointed rami, and tzvo-jointed fifth 

 feet. One member of this group has a one-jointed fifth foot, and 

 this is the only individual out of the thirteen that can be given any 

 place among species, i. e., C. phaleratns, as combining well recog- 

 nized species-characters. 



Three individuals constituting a fourth group combine the fol- 

 lowing characteristics : twelve-jointed antenncc, three-jointed rami, 

 and two-jointed fifth feet. These forms suggest C. varicans, 

 with which they have much in common, but from which they 

 differ considerably in detail. 



Some facts point to the probability that the Cold Spring Har- 

 bor forms with the ten-jointed antennae are morphologically unde- 

 veloped. Especially does the variation within the group consist- 

 ing of but few individuals point to the instability of these forms- 



What the true nature of these correlated peculiarities in Cy- 

 clops may be, can only be determined by following the life his- 

 tory of each individual. The relatively large size of these forms, 

 and the frequency with which they occur, as well as the con- 

 stancy of the correlated characteristics, suggest on first acquain- 

 tance with the Cyclopidae, that they represent distinct species, 

 but a fuller acquaintance warns us to look further for an expla- 

 nation of these most perplexing variations which are doubtless 

 largely due to the acquiring of sexual maturity while the mor- 

 phological changes in the body are still incomplete, and to the 

 varying external conditions to which they are subjected. 



BROOKLYN, NEW YORK, 

 March 30, 1903. 



