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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



win has come to the solution of heredity with his 

 theory of Pangenesis, which may be said to avail 

 itself of all that is reasonable and probable in 

 the explanations just discussed, and also to in- 

 clude several new and important ideas of which 

 the older theorists took no account. 



As paving the way for an understanding of 

 this and other explanations of the law of like- 

 ness, we may briefly glance at some of the chief 

 facts with reference to the structure and intimate 

 composition of living beings, with which micro- 

 scopic study has made us acquainted. When 

 the anatomist or physiologist seeks to unravel 

 the complications of human structure, or when, 

 indeed, he scrutinizes the bodies of all animals, 

 save the very lowest, he finds that each organ or 

 tissue of the body is composed of certain minute 

 vesicles or spheres, to which he gives the name 

 of cells. Cells, in fact, are the units of which the 

 bodily whole is composed. Nerves thus resolve 

 themselves, under the microscope, into fibres, and 

 the fibres, in turn, are seen to originate from 

 cells. Muscles similarly originate from muscle- 

 cells. Each tissue, however compact it may ap- 

 pear, is capable of ultimate reduction to cells of 

 characteristic kind. Nor is this all. The cells 

 themselves are in turn composed of smaller par- 

 ticles, and these smaller particles — of infinitesi- 

 mally minute size — may be regarded as consist- 

 ing, in turn, of the essential material of life — the 

 bioplasm or protoplasm — with the name of which 

 every one must be more or less familiar from the 

 part it has played in more than one grave biologi- 

 cal controversy. But the body of every living 

 thing is in no case stable, viewed either in its 

 chemical or in its more purely physical aspects. 

 It is continually, as the inevitable result of living 

 and being, undergoing change and alteration. 

 Chemical action is wasting its substance and dis- 

 sipating its energy with prodigal hand on the one 

 side, and rebuilding and reconstructing its parts 

 on the other. Its material particles are contin- 

 ually being wasted and excreted, while new parti- 

 cles are as incessantly being added to its frame. A 

 never-ending action of waste and repair is main- 

 tained within every living being; and it is not the 

 least striking thought which may ensue from the 

 study of such a subject that, notwithstanding 

 the constant renewal of our frames, we continue 

 to preserve the same recognizable form and feat- 

 ures. The development of new particles in place 

 of the old appears to follow the same course as 

 that whereby the first formed particles were 

 guided to their place in the developing young. 

 Germs, or " nuclei " — " germinal centres," as the 



physiologist terms them — are abundantly to be 

 descried within most of the tissues. Imbedded 

 among the fibres of muscles, for example, are to 

 be seen the germs from which new muscular fibres 

 will be developed ; and in the brain itself such 

 reproductive bodies are to be observed. Thus 

 the growth and continuance of our mental exist- 

 ence may be shown to be dependent on the pres- 

 ence of these new particles, which are destined 

 to renew in a material sense those powers which, 

 of all others in man's nature, most nearly ap- 

 proach the immaterial and spiritual. 



Nor, lastly, is the problem of existence and 

 structural complexity lessened in any degree by 

 the consideration that man's frame, as well as 

 that of all other animals, originates from a mi- 

 nute germ, composed primitively of a microscop- 

 ic speck of living matter, and exhibiting in its 

 earliest stages the essential features of one of 

 the minute cells or units of his tissues. Through 

 the powers with which this living germ-particle 

 has been endowed, it is capable of passing 

 through a defined series of changes, and of de- 

 veloping therefrom a being of more or less com- 

 plicated kind ; while the germ itself must be re- 

 garded as transmitting in some fashion or other, 

 and in a material form, the likenesses which link 

 parent and offspring together in so close and in- 

 timate a union. 



Applying the reasoning of the theory of pan- 

 genesis to the explanation of heredity and like- 

 ness in the light of the physiological evidence thus 

 briefly detailed, we are required to bear in mind 

 that, as an established fact, the cells of which a 

 living being is composed increase and multiply to 

 form tissues and organs, the new cells retaining 

 the form and essential characters of the parent- 

 cells. The cell, in short, is formed, is nourished, 

 grows, and reproduces its like, as does the body 

 of which it forms part. And botanists and zool- 

 ogists would inform us that lowly plants and ani- 

 mals, each consisting of but a single cell, not 

 only exist, but carry on the functions of life as 

 perfectly, when regarded in relation to the wants 

 of their existence, as do the highest animals or 

 most highly-organized plants. Each cell, pos- 

 sessed thus of vital powers, may further be re- 

 garded as correlating itself with the life of the 

 body at large, in that it is capable of throwing 

 off minute particles of its substance. These par- 

 ticles, named gemmulcs, may be supposed to cir- 

 culate freely through the system, and when duly 

 nourished are regarded as being capable of devel- 

 oping into cells resembling those from which they 

 were derived. These gemmules are further sup- 



