128 PHARMACEUTICAL BACTERIOLOGY 



kind of sperm cell will fuse with the egg cell is manifestly a matter of 

 chance. In some animals the male sex determinant is a double or fused 

 buL larger chromosome and again the male sex chromosome may be double 

 but remain unfused or uncombined. It is of interest to note that while 

 the male cell is as a rule much smaller than the female and suffers practi- 

 cally a complete loss of identity at the time of fertilization of the egg cell, 

 it is nevertheless the dominant factor in the transmission of hereditary 

 qualities. 



We may sum up the essentials of our present knowledge of cytology 

 as follows: 



1. The somatic cell preceded the germ cell, and all living cells and cell 

 units must have been derived from a plasm of somatic or trophic character. 



2. Gametes (both male and female) are merely differentiated somatic 

 cells of the same kind and are the product of extreme variations in the 

 environment. Germatic cells differ from somatic cells in the reduced 

 chromosomes. 



3. Germatic chromosomes as well as somatic chromosomes are living 

 plasmic complexes derived from the cell plasm. The plasm in all proba- 

 bility consists of and contains the ultimate units of living structure 

 which ultimate units are the creators and generators of the living formed 

 cell constituents of all kinds. 



4. Gametes have the property of combining or fusing certain sub- 

 stances which are believed to be more or less essential to the continued 

 septation of the egg-cell. Loeb and others have proven experimentally that 

 the male germ cell is not absolutely essential to embryonal development. 



5. The mitotic (karyokinetic) changes in the somatic cells manifest 

 some of the characteristics of the fusion of the gametic chromosomes. The 

 biological and physiological activities of the cell (microcosmj are very 

 closely analogous to the activities of the cells forming the body of the 

 individual (macrocosm). 



6. The biological association (symbiosis) of cells of the same somatic 

 origin (resulting from septation) in the multicellular organism, is an evolu- 

 tional incident, probably occasioned by the variations in the environment. 

 Associations of cells of this kind are in process of formation at the present 

 time among the Saccharomycetes, the group bacteria, the lower algae and 

 among the lower groups of the animal kingdom. 



7. We can readily comprehend how the originally homogeneous cells 

 resulting from septation, composing the complex organism, gradually 

 differentiated into tissues and organs each endowed with specialized 

 activities and functions. 



8. There are indications however, that the cells of certain organisms 

 are of heterogeneous origin. In the water net (Hydrodictyon) for exam- 



