THEORY OF SEX— ITS NATURE AND ORIGIN. 



"5 



to understand what the forms and phases of cells really mean. A 

 final corroboration of the cell-cycle, and at the same time a rationale 

 of it, is obtainable only on physiological lines, when we begin to 

 inquire into the protoplasmic processes which lie behind any change in 

 the form and habit of a cell. We have already spoken of the modern 

 physiologist's conception of living matter, or protoplasm, as an 

 exceedingly complex and unstable substance or mixture of substances, 

 undergoing continual chemical change or metabolism. On the one 

 hand, it is being continually reconstructed by an income of nutritive 

 material, which, at first more or less simple, is worked up by a series 

 of chemical changes till it reaches the climax of complexity and 



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Fig. 35. — Diagram of the Cell-cycle, — of encysted, ciliated, and amoeboid 

 phases. I., II., III., in Protozoa — IV., ovum and sperm of fern pro- 

 thallus — V., encysted, ciliated, and amoeboid animal cells — VI., ciliated 

 animal cell pathologically becoming amceboid — VII., sperm and amoe- 

 boid sperm — VIII., amoeboid and encysted ovum. — From Geddes. 



instability. These upbuilding, constructive, synthetic processes are 

 summed up in the phrase ' ' anabolism. ' ' But, on the other hand, the 

 protoplasm is continually, as it "lives," breaking down into more and 

 more stable compounds, and finally into waste products. There is 

 a disruptive, descending series of chemical changes known as kata- 

 bolism. Both constructive and disruptive changes occur in manifold 

 series. The same summit (see page 76) may be gained or left by 

 many different paths, but at the same time there is, as it were, a dis- 

 tinct watershed, — any change in the cell must tend to throw the pre- 



