1883.] 



Zoology. 



211 



dant and varies in size and particularly in color. So marked are 

 these differences that it would be difficult to believe at first sight 

 that they are not indications of specific distinction but these changes 

 are dependent upon food, light and other similar circumstances. 

 The typical form is found oftenest in rather large pools with no 

 outlet, but which do not actually dry up in summer. In length 

 the female is often i^^™' sometimes less and not seldom more. In 

 the smaller females the eggs are observed to be usually fewer, but 

 of the same size iJoo*™* to ^^- Recently, however in a small and 

 very shallow marsh which is frequently entirely dry, but which lies 

 near a less shallow pool swarming with the common Diapto- 

 mus (both being half a mile distant from any other water) we found 

 a new species of dimensions considerably exceeding those given 

 by Brady for var. Westwoodii-^. Closer examination showed that 

 the size and color were the only marked differences, antennae and 

 first pair of feet being identical, while the fifth pair of feet were but 

 little different and these differences were seemingly but the inten- 

 sifying of the characters of the smaller species to form the larger. 

 Here there were two pools, which within our personal recollection 

 formed but a single body of water and were now separated but by 

 a dozen steps, only differing as to depth and muddiness, in the one 

 of which flourished all stages of the ordinary form, while in the lat- 

 ter the one enlarged form alone existed. The conclusion is almost 

 forced upon us that the second pool needed only similar conditions 

 to bring forth this final stage of twice the usual size (but with eggs 

 but little larger — iJlo*'"^')- Shortly afterward the more shallow 

 pond dried up entirely so that no more of the larger form could be 

 obtained. 



It is not necessary to emphasize the fact that just such insignifi- 

 cant variations furnish the data upon which the generalizations of 

 modern science must stand or fall. A most interesting field is 

 open to any one with the opportunity to rear such forms as these 

 under conditions which can be altered at will in order to discover 

 what farther structural changes can be artificially induced. 



The practical value of the fresh-water copepods can hardly be 

 overstated since they are scavengers and almost entirely feeders 

 upon animal matter. The aggregate amount of putrid flesh which 

 the Cyclops fauna of a quart of water will consume is quite remark- 

 able, as any one may satisfy himself by watching the decay of such 

 a creature as a poUiwog in a jar of stagnant water. — C. L. Herrick. 



* Op. cit. p. 60. 



