242 FOUNDATIONS OF BIOLOGY 



typical mitotic figure. The two sets of chromosomes form an 

 equatorial plate at the center of the spindle, thus establishing 

 at once not only the mitotic apparatus for the first division 

 of the egg, but also the intimate association on equal terms 

 of chromosomes, with their potentialities from the two 

 parents, to form a common structure the nuclear complex 

 of the new individual. (Fig. 126, I, II.) 



Such are the outstanding facts of fertilization which a host 

 of investigators have brought to light chiefly within the past 

 century. It was not until 1839 that Schwann, with the es- 

 tablishment of the ' cell theory/ recognized the egg as a cell, 

 and sixteen years more before the sperm was similarly under- 

 stood; while the first realization that fertilization is an 

 orderly amalgamation of two cells to form one came during 

 the seventies of the past century. Then it became evident 

 that in sexual reproduction each individual contributes to 

 the formation of the offspring a single cell, in which must be 

 sought the solution of the problems of sex, fertilization, de- 

 velopment, and inheritance. However, the concentration of 

 attention on the cell has not simplified the solution of these 

 fundamental problems; but rather it has contributed to an 

 ever-increasing 'appreciation of the complexities of cell phe- 

 nomena and the difficulties of formulating them in general 

 terms. 



With a realization of the intricacies of the phenomena 

 involved and that they are cell phenomena, we may turn to 

 a consideration of the significance of fertilization. 



D. SIGNIFICANCE OF FERTILIZATION 



It may be emphasized again that fertilization is not repro- 

 duction. Reproduction, in the final analysis, is division 

 cell division or the detachment of a portion of the substance 

 of a living organism to constitute another. Rather is fer- 



