1 72 Wager: Movements of Aquatic Micro-Organisms. 
experimentally investigated may be mentioned the zoospores 
of Algae (green and brown), Euglena (green). Barnacle larvae 
(colourless), Volvox (green), Chlamydomonas (green), Phacus 
(green), Trachelomonas (green), Astasia (colourless), the zoo- 
spores of certain fungi (Chytridineae) and others, but Euglena 
viridis, a well-known organism found in stagnant water rich 
in organic matter, is particularly suitable for experimental 
investigation. It is often abundant in the liquid running from 
manure heaps, on which it forms a light green scum ; it is 
also plentiful on sewage farms. 
Euglena is capable of existing either in a motile or in a 
non-motile condition. In the motile condition it is a free 
swimming organism, spindle shaped, with an obliquely 
truncated fore end and a pointed posterior end (Fig. 1). The 
cell-protoplasm contains chlorophyll-bodies which may be 
scattered uniformly except for a clear space at the fore end or 
may radiate from the centre, leaving both ends free. Grains 
of a substance (paramylum) resembling starch but not coloured 
blue by iodine may also be found anywhere in the cell ; they 
are generally more numerous in the neighbourhood of the 
chlorophyll-bodies. A nucleus is usually seen near the 
hinder end of the cell. There is a mouth on the under side of 
the fore end, which leads by a narrow pharynx to a large 
internal cavity. A pulsating vacuole is present and there is a 
conspicuous red eye-spot on the dorsal side of the pharynx. 
Locomotion is effected by a single long flagellum, which 
drives the body forward by striking the water obliquely. 
The organism revolves on its longitudinal axis as it travels, 
taking a well-marked spiral path. 
The flagellum arises from the protoplasm on one side of the 
pharyngeal cavity, to which it is attached by means of a 
bifurcate base, and passes to the exterior through the gullet 
in close proximity to the red eye-spot. Just at the point 
where it passes the eye-spot, the flagellum bears a small 
refractive granule or swelling which is so placed that it is in 
very close contact with the eye-spot, but not organically 
connected with it (Fig. I.). 
The eye-spot is a very simple structure. It consists of a 
nearly circular layer of deep orange-coloured granules embedded 
in the protoplasm in close contact with the gullet around 
which it is curved. The granules are probably composed 
of, or closely related to, the pigment carotin. 
Lmder favourable light conditions, Euglena is nourished by 
the decomposition of carbon dioxide brought about by the 
light absorbed by the chlorophyll ; but under certain con- 
ditions, which are not clearly understood, when the light is 
weak and the Euglenae are in a good organic nutrient solution 
of potato-starch, the chlorophyll bodies in many individuals, 
Naturalist. 
