82 
nal pulse though there are slight traces of minor irregularities, and 
on September 7, 1897, a single unusual deyelopment of 58,000,000. 
Its optimum temperatures he close to the maximum heat of Summer 
months. It is found not only in water-bloom and plankton, but 
also along shores, on mud banks, and in sequestered pools and bays 
where temperatures reach 90° and over. Lightly colored and semi- 
transparent individuals of this and other species of the genus are 
found frequently in the plankton, suggesting an approach to holo- 
zoic nutrition in nature, such as Zumstein (99) has demonstrated 
experimentally in FE. gracilis. Euglena is quantitatively one of the 
most important links in the chain of food relations of the summer 
plankton, converting nutrient matters in the water, both organic 
and inorganic, into food for the Rotifera and Entomostraca of that 
season of the year. It in a measure replaces the diatoms, some of 
which decrease in number or disappear during the warmer months. 
Glenodinum cinctum Ehrbg.*—Average number, 1,360,192. 
This species is generally present from the middle of March till the 
end of September, though sporadic occurrences are found in winter 
months. There isa pulse on March 29 of 4,260,000 at a temperature 
of 49°, and another August 9 of 25,200,000 at 83°. This small 
planktont usually escapes through the silk net. It may be that 
several species have been included, as the conditions of plankton 
enumeration do not permit close scrutiny of such small organisms, 
lacking prominent structural characteristics. It seems to be a 
perennial planktont with a wide range of temperature adaptation, 
and with a growing period approximating that of the land flora of 
our latitude. 
Gomum pectorale O. F. Mull—This colonial flagellate has been 
found in the water-bloom in large nuinbers, especially in the back- 
waters. It was taken in the river plankton in 1897 and 1898 in 
May and again in August and September. These pulses coincide in 
location with those of Pandorina and Fudorina. 
Lepocincls ovum Ehrbg.*—Average number, 401,538; silk 
3,719. This species appears in the plankton in April and continues 
until the end of October, with sporadic appearances in winter 
months. There is no vernal pulse, and in both 1897 and 1898 maxi- 
mum numbers, 43,200 and 50,400, occur at the height of midsummer 
heat in August. In both years there are well-defined recurrent 
pulses at intervals of three to six weeks to be traced in the silk 
