ot. 
1883. ] Zoblogy. 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 ,°™- sometimes less and not seldom more. In 
the smaller females the eggs are observed to be usually fewer, but 
of the same size ,4™ to ;4°™ 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, antenna 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 a// stages of the ordinary form, while in the lat- 
ter the oze 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—,¥,e™). “Shortly afterward the more shallow 
pond pini up entirely so that no more of the larger form could be 
ned. 
_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- 
te, aS any one may satisfy himself by watching the decay of such 
a creature as a polliwog in a jar of stagnant water.—C. L. Herrick. 
THE SEGMENTATION OF THE VERTEBRATE Heap.—In a paper 
entitled “The segmental value of the cranial nerves,” published in 
ka Journal of Anatomy and Physiology, by A. Milnes Marshall, 
Me author gives a clear statement as to the theory of the segmen- 
Whon of the vertebrate skull, which was proposed by Gegenbaur, 
and is now generally accepted. While Oken, Goethe, Owen and 
Op. cit. p. 60, : ve 
