88 



ELEMENTARY ZOOLOGY. 



uals; and all organisms that grow old have the power of 

 giving to their offspring a new start in the matter of 

 growth and cell division. 



Just as is true of the other functions, reproduction in 



FIG. 15. Diagram illustrating indirect cell division. For the appearance of a 

 resting (undividing) nucleus see Fig. 2. A, coil stage, in which the most highly stained 

 protoplasm (chromatin) takes the form of a thread (cl); B, a stage in which the coil has 

 broken into numerous short loops (chromosomes, c.) scattered through the nucleus; C, 

 aster stage in which the loops come to be arranged in the equator of the nucleus; D, 

 diaster stage, in which each loop has split lengthwise, and the halves have moved apart 

 and are collecting about the two poles of the nucleus; E, later stage in which the chro- 

 matin is more compact and a new cell wall is being formed between the nuclei; F, 

 each daughter nucleus has gone into a coil stage, and the cell wall is complete. Each 

 nucleus next passes into a resting stage before dividing again. 



Questions on the Figure. Does this type of nuclear division 

 produce a more exact division of materials than the direct? In 

 what respects? Compare this figure with more complete ones 

 found in reference books. Enumerate the various happenings that 

 occur between the stage of the resting mother nucleus and that of the 

 two resting daughter nuclei. 



the lower forms is the function of the whole living animal. 

 There are no special organs; the protoplasm merely 

 divides. See Figs. 14 and 15 for the way in which this 

 division may come about. 



Even higher up in the animal kingdom the power of 



