Page:Popular Science Monthly Volume 90.djvu/106

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why it seems necessary for animals to die. This short scene (it lasts only fifty-live seconds) was most difficult to take. Three whole weeks of watchful wait- ing were required on the part of the photograph- er. He had to observe the ani- mals constantly and to be pre- pared to photo- graph the divi- sion when it oc- curred.

How the Yeast Cell Reproduces

Microscopic life re- produces not only by self-division but also by budding. To bring out that fact, the com- mon yeast plant, used in bread-making, was chosen by Mr. Stone as a motion-picture subject. The yeast is a one-celled plant. It reproduces by a process of budding which close- ly resembles the divi- sion which takes place in the protozoan. The yeast cells bud slowly. In order to secure a record of their growth, the photographs were made at intervals of four and one-half min- utes over a period of twelve hours. Since they are viewed at the rate of sixteen per sec- ond, the growth is wit- nessed in the short space of ten seconds.

The film next ex- hibits to us the repro- ductive processes of higher and more fami- liar plants. It shows that they reproduce their own kind either from cuttings or from seeds. A slip of gerani-

��Popidar Science Monthly

��Section of the film showing the devel- opment of a rat's embryo. All life develops from cells, in the same way

��um was planted. One photograph was made every six hours. On the screen a

��To the left is an enlargement of one of the hun- dreds of pictuics made to show the development of the rat from the embryo to the living litter. Since the rat is a higher animal and the processes of life are ex- plained from the crudest to the most complex forms, this por- tion of the film is near the end

��growth is shown in one second which took place in four days.

Most plants, how- ever, develop from seeds, and the seeds, in turn, originate in the flowers of the parent plant. To bring out that fact, photographs and diagrams of the sweet-pea are present- ed to show how the pollen grains from the anthers fall on the stigma and there pro- ceed to grow and send out tubes. The tubes work their way down through the coarse tis- sues of the style until they reach an ovule. Then the whole process of fertilization is re- vealed^how the fer- tilized egg cells become peas while the pistil of the flower becomes the pod which sur- rounds and shelters them.

Much more difficult was the problem pre- sented by the higher animals. With them life begins in a fertilized egg cell. The first ani- imal shown is the sea urchin, close relative of the starfish. On the

���The mother rat coming out of her box and picking up her progeny one by one in her mouth, dropping them into the nest

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