Russian type has thus been maintained from Novgorod to the Pacific, with but minor differentiations on the outskirts - and this notwithstanding the great variety of races with which the Russians have come into contact.
Discriminants.-The discriminant of a homogeneous polynomial in k variables is the resultant of the k polynomials formed by differentiations in regard to each of the variables.
The young cell-wall is always tenuous and flexible, and may remain so throughout, but in many cases thickenings and structural differentiations, as well as the changes referred to above, alter the primary wall considerably.
When present, the branchiae are generally differentiations of parts of the appendages, most often the epipodites, as in the Phyllopoda.
These two types are, in the main, correlated with two gradual differentiations in the minute structure of the thecal plates.