An American text-book of physiology . supplies this food to the growing cells. In lower forms of animal life, where eggs are fertilized outside the bodyof the parent in the water into which they are set free, they are usually pro-duced in enormous numbers. Some fail of fertilization, while others aredestroyed by enemies, and the large number is a compensatory adaptation bynature for their poor chance of survival. In mammals and man, however,ova have a much better opportunity of being fertilized and of developing intoadults, and their number is correspondingly reduced. Their relative fewness,as
An American text-book of physiology . supplies this food to the growing cells. In lower forms of animal life, where eggs are fertilized outside the bodyof the parent in the water into which they are set free, they are usually pro-duced in enormous numbers. Some fail of fertilization, while others aredestroyed by enemies, and the large number is a compensatory adaptation bynature for their poor chance of survival. In mammals and man, however,ova have a much better opportunity of being fertilized and of developing intoadults, and their number is correspondingly reduced. Their relative fewness,as compared with the spermatozoa, is in harmony with their larger size andthe fact that, wdiile awaiting fertilization, they are carefully protected withinthe body of the mother. Maturation of the Ovum.—Attention has been called to the maturationof the spermatozoon. The ovum undergoes an analogous process of ripening,which has been studied very carefully, and from its theoretical interest has 890 AN AMERICAN TEXT-BOOK OF
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