the greatest inequalities in numbers and percentages 

 at the various stations. Of 2 hauls made at adjacent 

 stations under almost identical conditions and with 

 only a comparatively short interval of time, the 

 total bulk of the sample sometimes varied from 1 to 

 several hundred cubic centimeters, and the percent- 

 ages from to 75 percent or more. If there is any 

 single characteristic of the macroplankton that is 

 more conspicuous than others, it is its consistent and 

 exceptional disparity of distribution. In view of this 

 fact it does not seem rational or even possible with 

 current methods to make any reasonable computation 

 of the amount of zooplankton per cubic liter of water, 

 or per square meter of the lake surface. More can 

 be accomplished, from both a biological and an eco- 

 nomic viewpoint, by a discussion of the distribution 

 of the separate species. 



A third fact is that the bulk of the macroplank- 

 ton varied greatly from month to month throughout 

 the survey. By adding the total catches at all of the 

 stations during each of the 4 months of the survey we 

 obtain figures representing the relative amounts of 

 the plankton in the lake during those months. These 

 figures express in cubic centimeters the total plank- 

 ton captured in the surface and bottom meter nets 

 during the month, and are: for June, 5, 464; for 

 July, 16,494; for August, 18, 921; and for Septem- 

 ber, 29, 136. A comparison of these figures shows 

 that the amount of plankton in the lake during July 

 was three times the amount in June, that it increased 

 slightly in August, and then increased 44 percent in 

 September. These 4 months are probably typical of 

 the entire year, and hence it is reasonable to sup- 

 pose that the amount varies also during the other 8 

 months. Whether the differences are as great as 

 those here recorded can only be determined by a 

 continuous collection of plankton throughout an entire 

 year. 



The fourth fact is established by the figures just 

 given, namely, that the amount of macroplankton 

 in the lake is amply sufficient to feed a much larger 

 number of fish than it now contains. When the sur- 

 vey first started each haul of the meter nets was 

 scheduled to last for 15 minutes. Two or 3 trials 

 were enough to show that the amount of macro- 

 plankton thus obtained was far greater than could be 

 adequately handled, and the haul was reduced to 

 5 minutes. Even after such a reduction the amount 

 of plankton in a single haul went beyond 1, 000 cc. 



several times and on one occasion reached 2, 000 

 cc. To those engaged in marine plankton investi- 

 gations, so great an amount obtained in such a short 

 time seems almost fabulous. It certainly proves that 

 the amount of fish food in this lake is so great that 

 the number of fish fry could be considerably in- 

 creased without fear of depletion. 



HORIZONTAL DISTRBUTION 



Attention is again called to the fact that the 

 present survey covered only the months of June, July, 

 August, and September, and hence the distribution 

 here given is for those months only. In the horizon- 

 tal distribution of the macroplankton, 3 zones can 

 be distinguished with considerable precision; marginal, 

 littoral, and lacustric. Of course along the margins 

 between them there is always more or less overlap- 

 ping of species, and migration back and forth from 

 one zone to another. But in general the zone limits 

 can be fairly well drawn, and each has its own char- 

 acteristic species as well as those common to other 

 zones. The marginal zone by virtue of its impor- 

 tance and the differences in the methods of collect- 

 ing and recording its plankton will be treated separ- 

 ately. The littoral and lacustric zones may well be 

 considered together since in the horizontal distri- 

 bution of the plankton they have much in common. 



The Marginal Zone 



In the preliminary reports of the work done in 

 1928 it was stated that very little attention had been 

 given to the marginal zone during that year, and it 

 was determined to remedy this during 1929. The 

 automobile trip around the margin of the lake was 

 planned and carried out for this purpose. The sta- 

 tions where marginal plankton was collected during 

 that trip are indicated upon the accompanying map 

 by triangles, while the steamer stations covering the 

 other 2 zones are represented by circles (fig. 57). 

 As a further means of distinguishing the two, the 

 marginal stations are lettered while the steamer sta- 

 tions are numbered. Inasmuch as the former were 

 all reached from the shore, they can also be con- 

 veniently designated in the text by the name of the 

 town, river, or creek where they were located. 



Regarding the places to be included in the mar- 

 ginal zone, we are met at once by the same question 

 that has confronted every investigator of lake plankton. 



147 



