176 DYNAMICS OF LIVING MATTER 



tration had been slightly raised, or which had been rendered slightly 

 alkaline through evaporation. In either case results such as he produced 

 may be observed. 



Max Cremer also obtained absolutely negative results when he 

 tried to cause the development of fish eggs with extracts obtained from 

 the sperm of the same species with the Buchner press. 



We may finally raise the question whether we can form, on the basis 

 of the facts mentioned, any idea as to how the spermatozoon causes the 

 egg to develop. From the facts stated in our fourth lecture in regard 

 to cell division it is obvious that the essential effect of the spermatozoon 

 consists in the transformation of part of the protoplasmic or reserve 

 material in the egg into the specific nuclein or chromatin substance of 

 the nucleus. In each nuclear division one half of the mass of each 

 original chromosome goes into the nucleus of each of the two resulting 

 cells. But during the resting period which elapses until these nuclei 

 are ready to divide again, each chromosome grows to its original size 

 again, and then a new division occurs. It is quite possible that the 

 oxygen which is required for the process of cell division is needed for 

 the synthesis of nuclein or chromatin substance. The fact that 

 the rate of development is influenced by temperature in much the 

 same way as are chemical reactions supports the idea given above 

 that the essential feature of fertilization consists in the starting or the 

 acceleration of a chemical reaction which is going on steadily in 

 the egg. 



It was natural to think first of the possibility that the spermatozoon 

 carries a positive catalyzer into the egg, and thus accelerates the above- 

 mentioned synthetical process, which might also occur in the unferti- 

 lized egg but too slowly to lead to any development. It occurred to me 

 that if this idea were correct the unfertilized eggs of the sea urchin'might 

 segment in normal sea water if they only could be kept alive for a suffi- 

 cient length of time. In order to test this idea I took out the ovaries with 

 bacteriological precautions and kept the eggs alive in sterile sea water 

 for a week. Not an egg segmented, but when sperm was added, seg- 

 mentation occurred promptly. This observation did certainly not 

 support my idea of the spermatozoon carrying a positive catalyzer into 

 the egg. It then occurred to me that a rise in temperature should act 

 like a spermatozoon, since a rise in temperature should accelerate the 

 velocity of chemical reactions. While a rise in temperature promptly 

 accelerates the development after the egg is fertilized, or caused to de- 

 velop by physicochemical methods, I have thus far not been able to start 

 development in this way. 



It then occurred to me that a superposition of two methods of fer- 



