THE MYCETOZOA 61 



The classificatory characters are mainly derived from the 

 sporangia, the capillitium (when it is present), and the spores. 

 Some species stand apart from their allies with great distinctness, 

 but in many genera examples intermediate in character between 

 the species are of common occurrence, and it is only by large 

 experience of the frequency with which the forms, as they occur 

 in nature, group themselves about certain centres that a correct 

 idea of the species can be attained. 



The distribution of most species appears to be, so far as it has 

 yet been determined, world-wide in the more humid parts of the 

 temperate and tropical- regions of the globe, where woodlands and 

 forests offer conditions favourable to their existence a fact which 

 is doubtless dependent on the ease with which the minute spores 

 are carried in currents of air. 



No Mycetozoa have hitherto been met with in a fossil state y 

 though from the degree of differentiation of the sporangia we cannot 

 doubt that the group is of high antiquity, and has in past time, as 

 at the present, played an important part in the disintegration of 

 vegetable tissues. 



It is remarkable that no parasitic organisms are known to live 

 on Mycetozoa, a fact which Stahl attributes to the readiness with 

 which foreign bodies are cast out by the organisms in the plas- 

 modial stage. 



In writing this account of the Mycetozoa constant reference has 

 been made to de Bary's classical work (1-3), to the papers of 

 Cienkowski (5-8), and to Zopf's treatise (24). But I wish especially 

 to acknowledge my obligations to the work of my father, Mr. A. 

 Lister, on their life -history and classification. So far as I have 

 been able to speak of the biological aspects of the group from my 

 own knowledge, it is mainly to the opportunities I have had in 

 following this work that I am indebted. The proof-sheets of this 

 article have been submitted to my father, and I feel that its- 

 authority is greatly enhanced when I add, as he allows me to do, 

 that the conclusions are in the main in accordance with his views. 



SUB -CLASS I. EUPLASMODIDA. 



The contents of the spores develop, on hatching, into flagellate 

 zoospores. Amoebulae completely fused to form the plasmodium, which 

 is the dominant phase of the vegetative period. 



DIVISION I. ENDOSPOREAE. 

 Spores developed within sporangia. 



COHORT I. AMAUROSPORALES. 

 Spores violet, or violet-brown. 



