534 



THE AMERICAN NATURALIST [Vol.XLIV 



the amoeboid swarmspores to form the Plasmodium of the 

 slime moulds has never been satisfactorily accounted for, 

 nor related to the processes either vegetative or sexual 

 in other groups of fungi. With the increase of our knowl- 

 edge of the possible variations which the sexual process 

 may undergo it is becoming more possible to accept the 

 conception that in some way the formation of the Plas- 

 modium may represent either an incipient or an aberrant 

 type of gametic union in which the normal fusion of two 

 gametes is replaced by a massing of indefinitely numer- 

 ous cells. 



The cytological study of the group is only just begin- 

 ning and doubtless much is to be corrected in the frag- 

 mentary observations already published. Olive, Jahn 

 and Kraenzlein, however, agree that there are evidences 

 of nuclear fusions either just before spore formation or 

 earlier in the formation of the fruit bodies, and that these 

 karyogamies are followed by synapsis and reduction 

 divisions. The figures given show that these forms have 

 typically developed nuclei which are favorable for fixing 

 and staining, and indicate that whatever disagreement 

 exists as to what occurs in the few types studied may be 

 expected to be cleared up by further work. 



The older authors were loath to regard the union of 

 the amoebae to form a Plasmodium as involving anything 

 of a sexual nature, but it is quite possible that we may 

 have to extend our conception of sexual fusions at least 

 in their primitive forms to include cases of multiple cell 

 fusions followed by vegetative growth, and finally the 

 fusion of the nuclei in pairs. That cell and nuclear fu- 

 sions may be thus widely separated is plain from the 

 conditions in the rusts, and in the slime moulds, as in the 

 rusts, nuclear fusion is followed shortlv bv the reduction 

 divisions. 



AVe can not yet regard the nuclear phenomena in the 

 slime moulds as sufficiently cleared up. In the light of 

 what has been found in other fungi there is however cer- 

 tainly no ground for believing that the nuclear history 



