OLD AGE AND DEATH 191 



the mother, a tadpole and, on very rare occasions, minute 

 frogs have been produced. In these cases the nuclei are always 

 smaller than normal and contain only one-half the normal 

 number of certain constituents of the nucleus, the chromo- 

 somes. Another curious fact is that by making sea water 

 markedly alkaline, the spermatozoa of more than one species 

 of star-fish were induced to fertilize the eggs of sea-urchins. 



Normal sexual reproduction involves the fusion of a 

 microscopic spermatozoon with an ovum which in many cases 

 is also microscopic. These exceedingly minute cells are the 

 carriers of heredity and within their small bodies are con- 

 tained the future characteristics, mental, moral and physi- 

 cal, of the resulting offspring. It is the fusion of these two 

 cells which produce not only the features which are common 

 to both parents, but also a combination of features due to the 

 mixture of their protoplasms and nuclei. Offspring resemble 

 their parents to a greater or less extent — "Do men gather 

 grapes of thorns, or figs of thistles? " But they also vary from 

 their parents to a greater or less extent and it is this variation, 

 which may be fixed and inherited "from one generation to 

 another," which leads to the establishment of new types in 

 the living world. 



Old Age and Death 



Life is a cycle, beginning with an egg and coming round in 

 time again to an egg. 



The fact that physiologically life is a wheel, a circle, a 

 cycle, is expressed by Sir Michael Foster in far better words 

 than I can command: 



When the animal kingdom is surveyed from a broad stand-point, it 

 becomes obvious that the ovum, or its correlative spermatozoon, is 

 the goal of an individual existence : that life is a cycle beginning in an 

 ovum and coming round to an ovum again. The greater part of the actions 

 which, looking from a near point of view at the higlier animals alone, 

 we are apt to consider as eminently the purposes for which animals come 

 into existence, when viewed from the distant outlook whence the whole 

 living world is surveyed, fade away into the Mkeness of the mere byplay 

 of ovum-bearing organisms. The animal body is in reality a vehicle for 

 ova; and after the life of the parent has become potentially renewed in 

 the offspring, the body remains as a cast-off envelope whose future is 

 but to die. 



