10 
I propose to test these theories by reference to certain organ- 
isms, as seen by the light of modern research. 
Volvox globator, is a plant possessing locomotion, and on that 
account regarded by the older Naturalists as an animal. Its 
surface is covered with vibratile cilia, by means of which it moves 
through the water; connecting these, are lines in which are certain 
Ameeba-like bodies. If we examine these Zoospores under a high 
power, we shall find they possess a red spot, which was considered 
by some Naturalists as an eye; they have also hollow spaces, or 
vacuoles, which possess the power of contracting at intervals of 
about 40 seconds; these contractile vacuoles much resemble those 
of the Amceba and lower animals. 
The plant called Hematococeus which covers stagnant water 
with a green scum in the spring, produces innumerable Zoospores 
similar to those of the Volvox and having like them a red speck. 
These, from their lively movements, have often been mistaken for 
animals. 
Presence of an Alimentary canal.—The Amoeba is an animal 
though having no Alimentary canal, and so imperfectly organised 
as to be compared to a living jelly without mouth, intestine, or 
stomach. 
The Gregarinida again are animals inhabiting the intestinal 
canal of worms, they have no mouth or organs, but absorb their 
nutriment from the juices in which they live. 
The diatoms which may be called single celled Algae with 
siliceous valves are known to possess the power of motion: some 
think the motion is produced by cilia, but Professor Max Schultze 
thinks it is caused by protoplasm flowing outside the frustule 
through the foramina which are so minute as to keep back the 
visible particles. 
Circulatory System.—We have already seen that this distinc- 
tion fails in the Amceba and the Gregarinida, and few of the lower 
infusorial animals possess it. Ehrenberg found that the food of 
many animalcules was collected in various receptacles, and assum- 
ing, though not proving, that these occupied a permanently fixed 
position, he gave the animalcules the name of Polygastrica. His 
theory however was based on insufficient evidence and soon had to 
give way. 
There is a notable circulatory process in some plants as in 
Nitella and Valisneria and in the hairs of the Tradiscanthia and 
Nettle. In these we see a circulation of fluid or spherical globules 
in a colourless fluid which follow a regular progression up one side 
of a cell and down the other. We have also undoubted evidence 
of the circulation of sap in all plants. 
A very similar circulation takes place in the stem of the 
Hydroid Zoophytes in which are found many resemblances to the 
