lO COLD SPRING HARBOR MONOGRAPHS. VII. 



seem to belong to a fixed type, and agree very closely with the 

 descriptions already given by earlier authors. 



Transitioial Stages of C. Sigiiatus, Coronatus. — Accompanying 

 the adult forms, are the later transitional stages of the species. 

 These are conspicuous both for their size and numbers. Atten- 

 tion has been called elsewhere (Byrnes, 1906)* to. the constancy 

 with which correlated characteristics occur in the young 

 of Cyclops. Plate III. reproduces two of the more striking correla- 

 tions. It shows that when the young have ten segments, or even 

 nine in the antennae, they have two-jointed rami in the swimming 

 feet. When they have acquired eleven segments in the antenn?e, the 

 rami of the swiinming feet have become three-jointed. /. r., have 

 reached their adult condition. 



The Figs, i, 5, and 3, Plate III., show, furthermore, that all the 

 characteristics common to the variety, the short second segment of 

 the antennule, the square basal segment of the fifth foot and the 

 inner fringe of hairs on the inner margins of the caudal stylets, are 

 often present in comparatively young forms. 



C. Signatus, var. oiiiniliconiis (also known as C. albidns 

 JuRiNE), Plate IV., is likewise very abundant at certain seasons in 

 the Long Island waters. It has been found in the greatest numbers 

 in cool, spring-fed pools. In general appearance, in color and in 

 the proportions of the body, aniiiiliconiis closely resembles coro- 

 natus, which it sometimes accompanies ; or it may be found with 

 widely different species. The characteristics by which anmdicornis 

 can be identified are first, a long second segment in the antennule ; 

 second, a relatively long basal segment in the fifth foot ; third, the 

 absence of hairs on the inner margins of the caudal stylets; and 

 fourth, the characteristic armature of the inner margin of the distal 

 segment of the inner ramus of the fourth swimming foot. In 

 coronatus this position is occupied bv two seta?. In aiiiutlicoruis 

 the more distal seta is greatly reduced or is wholly wanting, 

 its site then being marked by a cluster of very short hairs. 



The antennae of amiulicoDiis are characteristically long and in 

 their armature they resemble those of coronatus. 



* Byrnes, E. F. "Two Transitional Statfcs in the Development of Cyclops 

 Signatus, var. Coronatns." Biological f^uHrtin. vol. x., No. 5, April, 1906. 



