1904] CURRENT LITERATURE ~ 473 
taking care; and this involved an amount of pure drudgery which only one 
who has undertaken a similar piece of work can really appreciate. Yet one 
must confess to some surprise that after such an enormous amount of work 
in testing methods and in nde ese collections, the somewhat elaborate dis- 
cussion of the t trib of plankton should be based on only two 
sets of collections. 
At the close of the work the general results are summarized under twenty- 
six heads. In a brief review it is impossible even to state these, but refer- 
ence may be made to such as are of most general interest. The horizontal 
distribution of river plankton is practically unifor e maximum period 
of production is from April to June, but with great Festina Generally 
speaking, high water reduces the amount of plankton by dilution, and low 
water increases it by giving time for development of the various forms. So 
the more or less stagnant waters of the shallow lakes have a greater plankton 
productio 
eas things being equal, bodies of fresh water free from Spcapea 
(submerged macro-flora) produce more plankton than thos 
vegetation.” This statement, if prove en—and the author hate out a oni 
case—is a very important one. If it were shown, as it probably can be, that 
the reduction in plapkton in lakes with submerged vegetation is due to lack 
of plankton plants rather than to the small number of plankton animals, the 
generalization might go far toward explaining the eget fish production of 
shallow lakes. It has been shown by the reviewer that deep lakes produce 
more animal plankton per square meter than shallow ie and that the 
Il 
part of the plankton. It is the animal part of the plankton that furnishes 
most of the food for fish. The surplus of ny sane is simply waste. 
Hence, so far as food production is concerned, the s w lakes have no 
advantage over the deeper ones. But it is a matter v3 common sess 
that the shallow lakes, with submerged vegetation, are favorable to the pro- 
duction of fish. Is it not probable that the superiority of the ce lake 
over the deeper one is not in the greater amount of feiien but in that the 
submerged vegetation furnishes a favorable physical environment in which 
the fish may find hiding places? Probably the submerged vegetation does 
not remove from the water the part of the plankton that is important as food 
for fish, 
In comparing the plankton of the river with that of lakes, the author con- 
siders the river among the more fertile bodies of water. This fertility appears 
greater, however, because of the author's preference for stating plankton 
amounts in terms of cubic meters. This, of course, is a matter of personal 
preference ; the reviewer prefers to state it in terms of a surface unit, as did 
Hensen in his original plankton work. Especially, if one is to compare the 
fertility of a body of water with that of a piece of ground, the surface unit is 
the only practical one. 
