HETEROGENY AND VARIATION IN COPEPODA. l6l 



The Cyclops with the eighteen-jointed antennae agrees with 

 Clans' description of Cyclops clongatus, so far as Herrick has 

 quoted Claus. Nevertheless, its close agreement in all species - 

 characteristics with C. parcits, with which it was found, and the 

 very exceptional occurrence of so many antennal segments, make 

 it highly probable that we are dealing here with a case of vari- 

 ation rather than with a species-character. 



The Cyclops from Cold Spring Harbor, Long Island, were 

 collected at the surface of a very shallow pond along a road-side 

 near the laboratory of the Brooklyn Institute. The pond was 

 choked with water-plants and a scum of duck-weed floated on 

 the surface. From the extreme shallowness of the pond, any 

 life there must have been exposed to rapidly changing conditions. 

 The material collected in this pond was all taken from one 

 locality within a radius of a few feet, where the copepods were 

 in among the duck-weed. 



I attempted some statistical studies in variation on these forms, 

 but the work was soon interrupted by the comparatively small 

 number of individuals belonging to the same species, or to species 

 closely enough related to warrant any use of them in obtaining 

 data. Most of the forms I have been wholly unable to identify, 

 for while they agree with well known species in certain character- 

 istics, they differ from them in others which are apparently no 

 less important. 



Certain combinations of characters occur so frequently, that, 

 in the absence of transitional forms, one is often tempted to be- 

 lieve that in the bewildering array of forms before him, he is 

 dealing with new variations, of which it is almost impossible to 

 say whether they have a species value or not. Whether the 

 forms met with illustrate paedogenesis, or whether the season 

 was connected in any way with the morphological aspect of the 

 copepods, I cannot say, not having been able to collect from 

 this vicinity at any other season. But I have not seen any tran- 

 sitional stages in an individual such as would warrant the linking 

 of it with any well known species. 



One Cyclops frequently met with, combines the* following 

 characteristics: Antenna nine-jointed; rauu of siviinining feet 

 two-jointed ; rudimentary fifth foot one-jointed. 



