HUMAN HEREDITY. 363 



mentation, reproduction, etc. The reasoning already employed 

 leads us to conclude that these lower animals were the ancestors of 

 the higher, and transmitted to them- the qualities which the two 

 classes possess in common. For example, both the higher and 

 lower animals possess an alimentary canal — a tube running 

 through the body for the reception and digestion of food. We 

 conclude that this alimentary canal was not obtained by the 

 higher animals through external causes, but by inheritance from 

 the lower animals. 



We have, finally, to consider those qualities which man, and 

 both the higher and lower grades of animals, possess in common 

 with the very lowest animals. These lowest animals, consisting 

 in respect to their physical characters simply of minute jelly- 

 particles, destitute of organization, agree with the higher animals 

 only in their physiological properties. These are essentially only 

 two, nutrition and reproduction. These, indeed, are the two abso- 

 lutely fundamental and essential properties of any living organ- 

 ism. Without the one, the life of the individual ceases ; without 

 the other, the life of the species. From the biological point of 

 view, the carrying out of these two functions of nutrition and re- 

 production is the sole end of existence of any living being. Ani- 

 mals differ from one another — they occupy a lower or higher place 

 in the scale of life — according to the advantages of organization 

 enabling them to carry out these functions. The special powers 

 possessed by animals which at first sight seemed to be ends in 

 themselves, are seen by a moment's reflection to be only subserv- 

 ient to these two great ends. In birds, for example, both those 

 powers depending upon structural perfection, as flight, vision, 

 song, and plumage, and those depending upon a highly developed 

 nervous system, as the instincts of migration and nest-building, 

 serve, in the end, wholly to better enable the animals to maintain 

 their own life and that of their species — to carry out the functions 

 of nutrition and reproduction. Thus, rapid flight and keen vision 

 enable them to procure food ; melodious notes and brilliant plu- 

 mage are sexual attractions ; while migration and nest-building are 

 directly connected with nutrition and reproduction respectively. 

 From these considerations it is seen that, to the biologist, the 

 simplest animals — the animate jelly-particles — are beings of far 

 higher rank than their physical simplicity would indicate, since 

 they carry on the same life-processes that other animals do, only 

 lacking parts and organs subserving the operation of these pro- 

 cesses. It is, therefore, only to assume that like proceeds from 

 like to suppose that from these simplest animals the higher forms 

 received by the law of heredity the two powers of their being 

 which all possess in common — nutrition and reproduction. The 

 differences subsisting between these lowest animals and the higher 



