isa-normaladvance-1909-00176

Description:	during the last few years in regard to the importance of heredity.Even in ancient times men pondered over theresemblances and differences between parentsand their offspring, and wondered as to thehidden inner cause of the recurrence of characters in successive generations. But althoughthe general problem is an old one, its precisestudy is altogether modern. The earlier viewsof life and hence of genetic continuity werevery naive and crude. It was long believedthat living organisms could spring into existence spontaneously from lifeless matter and solong as this erroneous conception was adheredto, no real or substantial progress could be accomplished. The first step toward a clearerand better conception of life and hence of inheritance consisted in the overthrow of the olddogmatic theory of spontaneous generation.The dictum omne vivum ex vivo (all lifefrom life) is now universally recognized as thefirst law of living substance.We now know that all the living organismswhich inhabit the earth today are the directdescendants of pre-existing forms which resembled them more or less closely. That theorganisms that live today are the children ofa past generation and the parents of generations to come upon the earth. The life ofevery organism is of limited duration. It maylive for a day, a week, a month, a year, fiftyyears, a thousand or four thousand years, but itit is not immortal and some time it must growold, decline and die. The life of the species towhich the organism belongs is not, however, solimited. Geologic evidence teaches us thatthere are today species of plants which haveinhabited the earth for periods of time measured only by geological ages. Life is continuous, extending backward in point of time tothat remote and unknown period when vitalorganization first assumed its present form. Thedeath of the individual involves no break in theever recurring cycle by which the life of therace flows onward. The individual dies but itsprogeny survives and carries with it the inheritance of the race from which it sprang andpasses it on to its descendants.Death and destruction as well as growthand reproduction are continually taking placeand as a result about the same average quantity of living substance is maintained upon theearth. As growth and reproduction go on theliving substance must continually assimilatedead material. In spite of this perpetualchange it is nevertheless possible that a descendant may not contain a single one of thesame atoms that once formed a pan of a directancestor. Life may be compared to a whirlpool in a river into which material is constantly entering and as constantly passing on itsway. The whirlpool is always changing andyet it remains always the same. In the samemanner we believe that the peculiar propertieswhich characterize any given species are retained throughout successive generations andhanded on unchanged to their descendants.This is the law of genetic continuity. It restsupon the law of self-perpetuation, a law which,is as deep seated as life itself.Whenever or however we conceive life tohave originated upon the earth we must thinkof the substance manifesting it as having beenfrom the beginning endowed with the ability totake into itself nourishment, to grow, to reproduce itself and to vary, otherwise the great factof the evolution of the complex cosmopolitanlife of the present age could never have beenrealized.In the most lowly forms of life the body ofthe individual consists of a microscopic bit ofliving jelly known as protoplasm. Reproduction in such form is extremely simple, consisting of simple fission or bipartition. So far asany sort of examination the skilled microscopistis able to make, the two resulting pieces areexactly alike. This is, therefore, a case of perfect inheritance. If we conceive of one of theresulting organisms differing ever so slightly
Source:	http://indstate.contentdm.oclc.org/cdm/ref/collection/isuarchive/id/34206
Collection:	Indiana State University Archives

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