1 78 Wager . — The Life-history and 
always placed at the end of the zoospore immediately beneath the point of 
attachment of the cilium and in close contact with the nucleus. It is 
possible that the light rays absorbed by the oil-drop may be capable of 
setting up changes in its immediate neighbourhood, possibly through the 
nucleus, which are capable of reacting upon the cilium in such a way as to 
exercise a directive influence on its movements. 
Immediately the zoospores come to rest they round themselves off and 
begin to germinate. They increase slightly in size, and pseudopodia appear 
about i-| to 2 hours after they come to rest. The pseudopodia increase 
in length so rapidly that 3 hours after they begin to form many of them 
are five or six times the diameter of the cell. The germination follows 
the same course whether the zoospores are derived from asexual or from 
sexual sporangia. Figs. 49-53 show the early germination stages of 
a zoospore. 
Stained specimens show that the nucleus and oil globule are in close 
contact with one another and are surrounded by a deeply stainable 
chromidial mass (Fig. 48), the peripheral layer of cytoplasm being stained 
only very slightly. This chromidial mass thins out as it reaches the 
anterior end of the oil globule, and appears to be continuous with the cilium 
just at the point where it is given off from the zoospore. In the early stages 
of the growth of the young thallus, the chromidial mass persists around the 
nucleus and appears to be directly connected with the pseudopodia (Fig. 54). 
As development proceeds, the thallus assumes an irregular outline and the 
chromidial mass becomes alveolate owing to the appearance of globules of 
oil (Fig. 55). 
Reproduction. 
The organism reproduces itself sexually and asexually. So long as 
there is a fair amount of nutriment in the shape of unattacked Euglena 
asexual reproduction prevails, but as soon as the nutriment fails, and this 
happens very soon in an ordinary culture, the sexual organs begin to form. 
In both methods of reproduction sporangia are formed. In the asexual 
method the sporangia are produced directly, as outgrowths of the vegetative 
cells. In the sexual method of reproduction two vegetative cells unite to 
form a zygote, which subsequently on germination produces a zoosporangium 
similar in appearance but usually smaller than that formed asexually. 
The asexual sporangium first appears as a small spherical outgrowth 
on the vegetative cell. This gradually increases in size, and the protoplasm 
and oil-drops pass into it until nothing is left in the parent cell but a few 
delicate strands of protoplasm and one or two small oil-drops. From 
a series of observations made on two different sporangia, the rate of growth 
in length during the earlier stages appears to be about -005 mm. per hour, 
but in the later stages it varies very considerably, being often very much 
