iQoS] YAMANOUCHI— SPERMATOGENESIS AND OOGENESIS 1O5 



mentioned abov 



almost equal size at the time of union 



exceptional cases, 



tin of the two gamete nuclei takes place after the dissolution of the 



portions 



described among g}'mnosperms 



marked difference in size betw 



(M 



ERTSON 73), Sequoia (Lawson 59), Cryptomeria (Lawson 60), In 

 these species the sperm nucleus, being considerably, smalkr, becomes 

 imbedded in a depression of the egg nucleus. Howeverj the process 

 of their union does not differ essentially from the cases observed in 

 thallophytes and angiosperms^ because the chromatin material of 

 both gamete nuclei in resting condition fuses after the disappearance 

 of the contiguous part of the nuclear membrane. 



According to the accounts given by a number of authors there is 

 still another case: in Larix (Woycicki 99) and Taxodium (Coker 

 18), the gamete nuclei which come into contact do not fuse, but the 

 chromatin contents of both nuclei are kept in distinguishable maternal 

 and paternal groups; while in Pinus (Blackmax 8; Chamberlain 

 17; Ferguson 28) and Tsuga (Mfrrtll 63) the chromatin of 

 sperm and egg nuclei remains separate, forming two spire ms^ and only 

 after their segmentation into chromosomes are the two sets of struc- 



o 



first cleavasre soindle. In 



paternal chromatin within 



both maternal 



In the case of Nephrodium, as already described, the sperm which 

 entered into the egg nucleus was observed during a certain period 

 without any visible change, entirely imbedded within the chromatin 

 reticulum of the egg nucleus. The chromatin material which con- 

 stituted the body of the sperm begins to disintegrate, and the final 

 result is a reticular structure similar to that which we have noticed 

 in the nucleus of the spermatid before the formation of the sperm. 

 The reticular structures of both sperm and egg nuclei becon^ 

 anastomosed and mixed together entirely with in the membrane of 

 the e^ nucleus. The spirem of the first segmentation di\'isk>n is 

 organized from this reticulum as a continuous homogenous structure. 



This proce^ of disintegration of the body of the sperm within the 



