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Molds The Mother Cell: In yeasts and some molds the mother cell forms a small bleb at the surface, which grows rapidly to the size of the mother. A cross Wall then forms between the bud and the parent cell, and the bud breaks off to form a new individual.
filamentous Growth. The cells of some molds and algae are joined end to end in hairlike filaments. Growth occurs only at the tip of the filament, which elongates continuously. After the lip has grown a given distance, a cross Wall forms behind it to produce a new individual. Branching of the filaments can occur when the growing tip bifurcates and both branches continue to elongate.
Life begins with a single cell. This cell is so small that "one hundred could ride on an inch-long spider web." Yet in this single cell are the makings of a person. All the elements that heredity can give to the new individual are there, brought together by the union of one cell (the sperm) from the father with one cell (the ovum) from the mother. Within this fertilized cell are twenty-four different pairs of chromosomes, one of each pair given by the mother, one by the father. Within the chromosomes are invisible particles called genes. These genes, together with other gene-like substances, are handed down from the parents to the child; they determine the individual's hereditary tendency (36,1949).
Molds may be made of Flexible materials such as glue, gelatin, rubber or agar compositions, or they may be rigid of plaster of paris, terracotta, sand, metal, etc. Flexible molds, first developed about the middle of the 19th century, are especially useful for the casting of intricate forms with undercuttings. The older, traditional methods of casting employ rigid molds which may be either waste molds or piece molds.
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