160 General Biology 



mentioned, several hundred times, until this same conjugation or joining 

 process occurs again. The larger stainable spot is dissolved at the time 

 of conjugation and is. thought to have some nutrient function. 



It is the nuclear material which seems to be the important physical 

 matter in the formation of any living thing — plant or animal — and, in 

 turn, it is only the colorable matter inside the nucleus known as chro- 

 matin, which breaks up and divides (the separate parts are now called 

 chromosomes), and is carried on from parent to offspring. The chromo- 

 somes are now considered the most important factors which throw light 

 on the many problems of inheritance — that is, on all problems pertaining 

 to characteristics actually obtained from our parents, whether these are 

 physical, emotional, or intellectual. 



It is, therefore, of decided importance that we obtain a clear con- 

 ception of chromosomes, because in the final analysis every detail of 

 what we are and can be, that has any relation whatever to our physical, 

 emotional, and mental makeup, must come from our parents through 

 the chromosomes in the egg cell of the mother and the sperm cell of the 

 father. In other words, the chromosomes that were ours at the moment 

 of mixture of sperm and egg, possessed the sum total of all the factors 

 producing the physical, mental, and emotional endowment with which 

 we were possessed when ushered into the world (except the food and 

 environment needed for growth, and a place to grow). 



In Paramoecia, the animal does not inherit anything from its parent 

 — it is half of its parent. Each Paramoecium is thus equivalent to an 

 egg cell or a sperm cell. The offspring is not a chip from the old block — 

 it is half the block. 



An interesting application follows : 



In every living thing, where observation of chromosome material 

 has been possible, life begins from a single cell of some kind. In the 

 higher forms, this (egg cell) receives one half the chromosomes from 

 the sperm after the egg cell has cast out one half of its own chromo- 

 somes. There is thus a constant trend toward forming an individual 

 who approaches the average individual of the species to which each such 

 individual belongs, for, each new living thing is made up of one half 

 the chromosomes which the maternal egg cell possessed, and one half 

 of those which the paternal sperm cell contained. 



If this were not so, then those cases in the animal world which 

 have virgin birth, would have an ever lessening quantity of the chromo- 

 some material in each next generation. Each offspring would then 

 become more unlike its parent, until in time, when no fertilization takes 

 place to restore the proper quantity of chromosome material by a pater- 

 nal sperm cell being added to the maternal egg cell, the offspring would 

 not be recognized as a member of the species to which its ancestors 

 belonged. 



In every female, in the higher forms, at the time of birth the sub- 

 stance of the germ tract is already segregated so that practically every 

 egg in her body that she will ever have is present. This is as true of 

 a bird as of a human being. The human has about 35,000 eggs in each 



