7i8 



PROTOZOA. 



there is little doubt that Radiolaria abounded in the seas where the great 

 Chalk beds were deposited, they are not found in chalk; their siliceoua 

 skeletons probably having been dissolved and re-deposited as flint. 



In the next division of the Protozoa, we find animals in which the proto- 

 plasmic processes of the body are still further specialised. They no longer 

 send out indefinite pseudopodia for creeping slowly along 

 The Flagellata. on the surface of the ground, nor do they float free in the 

 water, the protoplasm streaming out on all sides in fine 

 rays. We now have only one or two processes adapted for locomotion through 

 the water, and these are long and whip-like. These whips or "flagella," at 

 the anterior end of the body, by their constant movement, drag it along 

 rapidly through the water. 



Some of the simplest of these Flagellata are so very like vegetable cells, 

 that they were long excluded from the animal kingdom. It ia, indeed, 

 impossible to draw any very hard and fast line between the lowest plant and 

 animal cells, and, as authorities are still more or less divided in opinion, 

 such simple Flagellates may be regarded as belonging to a border land. 

 One point in which many of the Flagellata resemble vegetable cells 

 is colour. The Protozoa of other divisions are usually colourless and 

 transparent, whereas many Flagellates are of a bright red, yellow, brown, 

 or green. Some of the simplest of these animalcules (Fig. 6, A) as they 

 dart across the microscopic field by the help of their whips, which, on 

 account of the rapidity of their movements are for the time invisible, 



sparkle like minute emeralds. Some of 

 the red Flagellata, when swarming in 

 great numbers, produce large red 

 patches on the sea. Other forms shine 

 with phosphorescent light, and cause 

 the beautiful glow often seen among the 

 breakers on a shore at night. Thirty 

 thousand animalcules are said to be 

 contained in one cubic inch of such 

 phosphorescent water. 



Some of the Flagellata are distinguished 

 by a collar-shaped projection round the 

 depression from which the whip-like 

 appendage rises (Fig. 6, D), others by 

 taking in food at one spot only of the 

 body, i.e., at the base of the chief whip 

 (C). A shelly covering is present in 

 some forms, in which it may resemble a cuirass or may be prolonged into 

 several sharp, horn-like processes (E). These horny cases are often found in 

 Chalk rooks. 



The Flagellata do not always, like the creatures we have hitherto described, 



lead independent lives, each individual feeding, moving, etc., on its own 



account. They are often found grouped together in 



Flag'ellate colonies, the various individuals composing the colony 



Colonies. being united by a common mass of protoplasm. The 



manner in which such colonies arise is interesting and 



important, inasmuch as, from this primitive grouping of single cells to form 



simple colonies, complex and highly organised colonies arosej culminating in 



the bodies of the higher animals, which are in reality gigantic colonies of 



Fig. 6.— Flagellata. 

 A, Euglena. 

 i?. Chilomonas. 

 C, Noctiluca. 

 J), MonoBiffa. 

 -£', Ceraliuni. 



