122 AMPHIMIXIS OR ESSENTIAL MEAiVING OF [XII. 



unknown that the mother-cells of ova contain twice as many 

 nuclear rods as existed in the primitive egg-cells. Until this was 

 known, the ' reducing division ' was only required to effect a 

 halving of the nuclear substance, and for this purpose one 

 division would be sufficient. We now know that a second 

 division is rendered necessary because the number of the rods 

 is doubled before the process of reduction has begun. The 

 object served by this doubling remains an obscure point 

 upon which even the spermatogenesis of Ascan's does not at 

 present enlighten us. My previous interpretation of the first 

 polar body as the removal of ovogenetic nucleoplasm from the 

 egg must fall to the ground : about this there is no possible 

 doubt, but how can we better explain the necessity for two 

 divisions? Why should the nuclear substance be doubled, 

 only to be halved again ? O. Hertwig has also propounded 

 this question, but so far without being able to supply an answer. 

 He hopes that a more accurate study of the manner and method 

 of the arrangement of the chromatin elements in the two succes- 

 sive divisions will ultim.ately lead to a deeper knowledge of the 

 essence of the whole process of maturation. I also hope the 

 same. The processes which bring about the doubling of the 

 chromatin rods in the resting nuclei of ova and sperm-mother- 

 cells, contain, without doubt, the key to an understanding of the 

 necessity for this increase in number, which at present appears 

 to be so mysterious and superfluous. 



Whether unaided observation will ever succeed in making 

 clear the accessory processes, in other words, whether morpho- 

 logical events can be followed in minute detail so far that we 

 can wrest from them the secret of their meaning, we cannot 

 say. Without some guiding idea, it is scarcely possible that the 

 observations of investigators could be directed to the most 

 essential part of the process, especially in this case, where 

 differences of substance are probably present — differences 

 which might be invisible, but are perhaps capable of being 

 inferred by processes of reasoning. 



Thus it may be possible, on the basis of Hertwig's observa- 

 tions, to penetrate somewhat deeper into the meaning of the 

 remarkable processes which attend the ' reducing divisions,' if 

 only the subject be attacked from the point of view of the theory 

 of ancestral germ-plasms. 



