Tlic Life-liistorij of Mycetozoa. By G. Lister. 365 



or their nuclei." In the mosaic stage each cell contains a single 

 nucleus which passes into the young spore, where it undergoes 

 two mitotic divisions * ; thus the four nuclei of the mature spore 

 are produced. 



We may briefly review the development of Ceratiomyxa, and 

 compare it with one of the wood-inhabiting species of the Endo- 

 sporefe. In both the plasmodium emerges in the form of 

 cushions of jelly to fructify in the open air. In both the nuclei 

 undergo a reduction division before spore-formation. By a stretch 

 of imagination, the sporophore in the mosaic stage might be 

 regarded as a sporangium with an evanescent or undeveloped 

 wall, and with a large gelatinous columella, over whose surface 

 the spore-cells form only a single layer. But after this stage all 

 attempts to make the two life-histories correspond fail. In the 

 outgrowth of the spore-cells to form stalked spores Ceratiomyxa 

 shows a unique arrangement ; moreover, in these spores a remark- 

 able process of what may be called precocious development occurs, 

 by which each mature spore contains four nuclei, and these, on 

 germination, at once divide again to take charge of the eight 

 flagelluhe into which the spore-contents separate. In the 

 Endosporea3 the increase of eight flagellul?e from one spore is 

 arrived at leisurely and after repeated intervals of feeding. Thus 

 although Ceratiomyxa is undoubtedly one of the true Mycetozoa, 

 it holds a curiously solitary position, apart from all other species 

 of the group. 



In conclusion I wish to express my indebtedness to Dr. Jahn 

 for his courtesy in lending me the preparations from which the 

 drawings on PL XI were made. I have also to thank Mr. J. H. 

 Mummery for allowing his beautiful photograph of Ceratiomyxa to 

 be reproduced on PL X. 



* These divisions are well illustrated by E. W. Olive (1907), " Cytological 

 Studies in Ceratiomyxa." Trans. Wise. Acad. Sci., sv. pi. xlvii. figs. 11-14. 



