/ W. X. 4 //>/-//, 1906. No. 



BIOLOGICAL BULLETIN 



TWO TRANSITIONAL STAGES IN THE DEVELOP- 

 MENT OF CYCLOPS SIGNATUS, 

 VAR. CORONATUS. 



A PRELIMINARY NOTE. 



ESTHER F. BYRNES. 



While studying some of the inhabitants of a pool of spring 

 water at Cold Spring Harbor, Long Island, during the months 

 of July and August, I was perplexed by the constant occurrence 

 of two comparatively large Cyclops that I was unable to identify 

 as belonging to any known species. 



The prevalent adult forms in the pool were C. sigiiatus var. 

 tcnnicornis (annulicornis} and var. coronatus and C. scrntlatus. 

 That the forms in question bore no relation to C. scrntlatus was 

 quite evident. In certain characteristics they agreed with C. 

 sigiiatus but for some time I hesitated to associate them with 

 C. signattis because of constant correlations in structure, and 

 because the larger of the two forms was occasionally found to be 

 sexually mature. 



The smaller of the two cyclops, Plate VII., combined the follow- 

 ing characteristics : the antennas usually contained ten segments, 

 but occasionally nine segments were present ; the rami of the 

 swimming feet were two-jointed, with an armature that indicated 

 immaturity as follows : 



First Foot. Second Foot. 



'93 



