MYCETOZOA 159 



utricularis are ovoid or globular, of a grey or iridescent violet 

 colour, clustered and borne on membranous straw-coloured 

 branching stalks. The capillitium is a network of flat bands, 

 with broad thin expansions at the angles, and lime granules 

 evenly distributed through the strands. The spores them- 

 selves are from 9 to 12 p in diameter, of a bright brown colour. 

 After some time the external wall of the sporangium breaks 

 down, and the spores are exposed hanging on the threads of 

 the capillitium. They are gradually scattered and disseminated, 

 and if kept dry retain their vitality for an almost indefinite 

 time. But if they are wetted the spore coats are ruptured, and 

 their contents emerge as a number of pellucid globules, which 

 lie quiescent for a few minutes and then begin to put forth 

 pseudopodia and exhibit amoeboid movements. A few minutes 

 more and each animalcule becomes pear-shaped, develops a 

 contractile vacuole, a single flagellum at its narrow end, and 

 swims off with a dancing movement, the flagellum at the 

 narrow end being in advance, whilst pseudopodial processes 

 are given off from the broad posterior end. These active 

 bodies are known as flagellulse, and they feed actively on 

 living bacteria caught by the pseudopodia at the hinder end. 

 The flagellulae, if well fed, multiply rapidly by binary division, 

 but after a time they become sluggish in movement, withdraw 

 their flagella, and creep about by their pseudopodia. In this 

 condition they are known as amcebulae. When two amcebulai 

 come into contact they coalesce, the protoplasm of the two 

 running together, whilst the nuclei remain separate. Other 

 amcebuke are attracted to the spot, often in great numbers, and 

 after a time the cytoplasm of all becomes confluent, and a new 

 plasmodium is formed. It should be noticed that the union 

 of the amcebulae to form a plasmodium is not a case of 

 conjugation but of plastogamy, for there is no union of nuclei 

 but only of cytoplasm. On the other hand, it is clear that 

 the fusion of the nuclei of the sporoplasm in pairs previous to 

 spore formation in Arcyria is a true process of conjugation. 

 Furthermore, if the somewhat fragmentary accounts of the 

 heterotype mitosis immediately following conjugation are 

 substantiated by further research, the highly interesting fact 

 will be established that in Mycetozoa only half the full 

 number of chromosomes are present in all the numerous 

 nuclear divisions intervening between the amcebula stage and 



