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VII 



Reproduction 



REPRODUCTION is Ordinarily thought of as an extremely complex phe- 

 ^nomenon coupled as it is, sometimes, with spermatogenesis, oogenesis, 

 reduction division, copulation and fertilization. It becomes less complex in 

 appearance, at any rate, when we review the process in simple plants and 

 animals. Sexual reproduction in Farmnecium, for example becomes simply 

 the side by side conjugation of two specimens with the subsequent ex- 

 change of nuclear material. 



When we examine some of the numerous instances of reproduction 

 in which no sex is involved, a type known as asexual reproduction, the 

 matter appears very elementary. In bacteria the cell simply divides into 

 two equal parts and each half then proceeds to grow into an adult bac- 

 terium. In yeast tiny protuberances called buds appear on the parent cell, 

 grow larger and eventually detach themselves or break off. 



One aspect of this subject which needs amplification is that reproduc- 

 tion is the process by which immortality is attained. At first this may sound 

 fantastic but if one considers that tiny bits of living matter passed on to 

 the offspring from the parents in the form of eggs and sperms are lineal 

 descendents from similar structures passed on to them from their par- 

 ents and so on back to the dawn of man's emergence from pre-man, the 

 thought soon loses its aspect of improbability. 



When we list the characteristics of life we frequently mention re- 

 production as one of the main features distinguishing it from the inorganic. 

 Stones do not beget stones nor does a piece of iron ore divide into two 

 pieces of ore, except by fracture. The dividing line is not as sharp as 

 formerly thought. Protein molecules as found in a piece of dried beef are 

 still protein molecules but they do not reproduce themselves. The es- 

 sential part of chromosomes, the genes, are now thought by many to be 

 large complex protein molecules and yet these do duplicate themselves 

 every time a chromosome divides lengthwise in cell division. The dif- 

 ference here seems to be that a living system is necessary in conjunction 

 with the molecules. That brings us back, of course, to the nature of life 

 and the student will observe that we have described a neat httle circle and 

 are now back to the same relative position where we were when we 

 started this discussion. Someday the answer will be forthcoming; some- 

 day all the proper types of bricks will be assembled, the bricks repre- 



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