UNION OF THE GERM-CELLS 



207 



The above data are drawn from sources so diverse and show so 

 remarkable a uniformity as to establish the general law with a very- 

 high degree of probability. The few known exceptions are almost 

 certainly apparent only and are due to the occurrence of plurivalent 

 chromosomes. This is certainly the case with Ascaris {cf. p. ?,y). 

 It is probably the case with the gasteropod Arion, where, as described 

 by Platner, the egg-nucleus gives rise to numerous chromosomes, the 

 sperm-nucleus to two only ; the latter are, however, plurivalent, for 

 Garnault showed that they break up into smaller chromatin-bodies, 

 and that the germ-nuclei are exactly alike at the time of union. We 

 may here briefly refer to remarkable recent observations by Riickert 

 and others, which seem to show that not only the paternal and mater- 

 nal chromatin, but also the chromosomes, may retain their individu- 

 ality throughout development.^ Van Beneden, the pioneer observer 



1 '89, pp. 10, zz- 



