. Il microscopio; un semplice manuale. Microscopi. 132 IL MICROSCOPIO creatura, lias anche un grande disco-come superficie dove vi è prac- tically no sldii al suo jelly. Le ciglia che vibrano intorno a questo disco causa un potente flusso di corrente ed è sorprendente per guardare i piccoli tipi di protozoi essendo hustled nella creatura del corpo, dove nuotano per circa un secondo o due e sono quindi ancora. Come fase finale troviamo le creature con un solo piccolo open- ing dove il cibo può essere assorbita e il completo sviluppo della bocca è qui concluso. In una delle precedenti figure mostra la dolce l

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. The microscope; a simple handbook. Microscopes. 132 THE MICROSCOPE creature, lias also a large disc-like surface where there is prac- tically no sldii to its jelly. The cilia which vibrate around this disc cause a powerful current to flow, and it is amazing to watch the smaller kinds of Protozoa being hustled into the creature's body, where they swim about for a second or two and are then still. As a final stage we find creatures with only one small open- ing where food can be absorbed, and the complete development of the mouth is here concluded. One of the earlier figures shows the dainty little Collared Monad, which consists of a single cell with a vibrating whip, or flageUum, and a very perfect little cup or collar of transparent material. They are often found in large colonies on the surface of weeds. To them we owe our sponges. A microscopic examina- tion of one of the holes of a growing sponge reveals a colony of these little organisms, closely arranged aU round the interior of its surface. These have the power of creating instead of shells a fibrous material, which forms the matrix in which they are embedded. In place of shells they deposit hard, flinty spines in the substance of this matrix, and these are called spicules. Thus a sponge consists of myriads of colonies of Collared Monads, their vibrating flageUse causing a current of water to rush through every cavity of the entire sponge, in order to provide the food and oxygen necessary Fig. 128.—Sponge. for the support of the community. The Protozoa show in a series of inter- esting stages the gradual development of creatures of one cell. Each ceE is complete in itself, though, as in the case of the sponge, an approach to a more elaborate form is seen. Never- theless, here each organ eats for itself, breathes for itself, re- produces itself by splitting in half, and is an individual. Later stages of development show creatures of more than one cell, in which some cells perform one function and some anoth

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• bookcentury1900
• bookdecade1920
• booksubjectmicroscopes
• bookyear