20 THE NEW CELL DOCTRINE 



study the phenomena with the microscope we are unable to 

 observe that anything is given off from the spermatozoon to 

 the ovum. The changes in the ovum, therefore, by which 

 other spermatozoa are excluded depend upon minimum 

 quantities. 



Teleology, or the adaptation to an end, rules all living 

 bodies. Accordingly we must assume a priori that the 

 limited size of cells is a purposeful adaptation. It is probable 

 that the size of the cells is favorable to the metabolism which 

 occurs chiefly in protoplasm. It depends on the one side 

 upon the surface of the cell, and on the other upon the nucleus, 

 which must itself be nourished and also supply material to 

 the cell body. Therefore it is important that the distances 

 remain small. As an example of the relation of the nucleus 

 to the differentiation of protoplasm, I wish to cite the investi- 

 gations of Eycleshymer 6 on the development of muscle fibers. 

 The work was done in my laboratory. He observed that the 

 mass of chromatin increases in the nucleus of very young 

 muscle fibers, and that thereafter the formation of the muscle 

 fibrils begins. As the development of the fibrils progresses, 

 the amount of chromatin in the nuclei diminishes, Fig. 

 13. It is clear that the chemical combinations are distrib- 

 uted through the protoplasm chiefly by diffusion, a slow 

 process. Hence the great importance of the small dis- 

 tances. A more exact conception of this we may gain from 

 the investigations on the early development of pigeons, 

 which have been carried out at the University of Chicago, 

 at the suggestions of Professor Whitman. 7 The egg of the 

 pigeon, like most other eggs, is fertilized by a single spermato- 

 zoon. The influence of this does not at first stretch very far 

 in the ovum, so that the territory which we may designate as 

 saturated is small. All around this territory we have, so to 



