5dD 
vegetation, in which green flagellates and small alge and dia- 
toms are most abundant numerically, and, therefore, quanti- 
tatively. Moreover, in 46 of the 105 instances the movement 
in production, as shown in the rise and fall of the plankton 
taken by the filter-paper and silk net, is in the same direction, 
though amplitudes reached are rarely proportionate. The co- 
incidence is most marked when the catches of the silk net re- 
veal changes in production of considerable magnitude, as, for 
example, during the rise and fall of the vernal pulse in 1897 
and in 1898, and during the winter changes of 1898-99. There 
are suggestions in these records of vernal pulses of considerable 
magnitude, of a large midsummer production, and of a great 
development in the low water of 1597, when an enormous 
growth of Chlamydomonas turned the river to a livid green, and 
contributed to the maximum filter-paper record of 119 em.‘ per 
m.*, 14-fold the coincident catch (8.47) of the silk net. There 
is also, even in these erratic data of the filter-paper catches, 
some evidence of the pulse-like character of the production of 
these minute organisms which form the greater part of the 
catch. This appears often to be coincident with the cycle 
movement in the volumetric data of the silk net, and may best 
be seen in the records of the winter of 1898-99. The enumer- 
ation confirms beyond all question the existence of these recur- 
rent pulses, dimly suggested in these volumetric records. The 
spring and summer plankton which leaks through the silk is 
largely made up of small alge, flagellates, and diatoms, with 
some ciliates, principally Codonella, and rhizopods. The winter 
plankton thus lost is largely composed of broken colonies of 
Synura, together with many predatory and elusive Jnfusoria, 
largely representatives of the Holotricha, which multiply abun- 
dantly with the autumnal increase in bacteria. 
It can be apparent to no one more than to the writer that 
such data as these are unsatisfactory in determining the pre- 
cise volumetric extent of the leakage through the silk. That 
this leakage is, however, beyond all question considerable must 
become evident to any one who actually works over collections 
