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THE AMERICAN NATURALIST [Vol. XLIV 



ment for which we have no satisfactory account of the 

 chromatin. The coarse reticulum of the egg nucleus is 

 not chromatin, for most of it may remain after chro- 

 matin again becomes demonstrable. To say that the 

 chromatin becomes dissolved in the linin or takes the 

 form of coarse granules or nucleoli, which may or may 

 not be chromatin at all, hardly solves the difficulty. That 

 some of the so-called metaplasm has about the same 

 position as the latest recognizable stages of the spirem, 

 seems to be about all that can be said. It is certain that 

 chromatin has not yet been traced from the telophase 

 of the ventral canal cell mitosis to the resting egg 

 nucleus with any such certainty as in the pteridophytes 

 and angiosperms. The organization of the spirem from 

 the dubious contents of this nucleus has not been traced 

 in any satisfactory way. However, it is perfectly cer- 

 tain that a small and beautifully definite spirem finally 

 appears. 



Fertilization 



To the cytologist, who is likely to attribute extreme 

 importance to chromatin, these reduction series in the 

 formation of eggs and sperms are very important, since 

 the more there is eliminated from the structures taking 

 part in fertilization, the more accurately can we deter- 

 mine what is essential and what only accessory. 



Fertilization has been studied more thoroughly in 

 Pinus than in any other gymnosperm. Here each arche- 

 gonium has its own archegonial chamber and the pollen 

 tube entering it necessarily discharges its contents into 

 the one egg, the two male nuclei, together with the stalk 

 and tube nuclei and also more or less cytoplasm and 

 starch all entering the egg. One of the male nuclei comes 

 into contact with the egg nucleus and the nuclear mem- 

 branes at the point of contact break down, so that the 

 chromatin of the two nuclei becomes surrounded by the 

 membrane of the egg nucleus. A spirem is formed from 

 the chromatin network of each of the sex nuclei and each 

 spirem segments into 12 chromosomes, so that there are 

 twenty-four chromosomes. These do not fuse with one 



