80 h. marshall ward. 



Division. 1 

 It is easy to convince one's self of the fact that the myxamcebee divide. 

 I have several times observed this process directly and in detail ; but 

 it might also be safely concluded from the fact that in sowings of from 

 8 or 9 to 20 or 30 spores, which yielded twice that number of myxa- 

 moebee on germination, it was frequently observed that the number of 

 myxamcebse increased several fold in the course of two or three days. 

 In figs. 19 and 20, however, are drawings of the process as actually 

 observed in successful cultures. A myxamoeba was detected in the con- 

 dition at a (fig. 19) at 10.48, having become extended and slightly 

 constricted in the middle, where it was relatively at rest, though 

 several small pseudopodia were being protruded and withdrawn at the 

 ends. No nucleus was detected, but two pulsating vacuoles were 

 clearly visible. Two minutes later the constriction had deepened con- 

 siderably, and at 10.52 (two minutes later still) it had cut the mass 

 in two (fig. 196 and c), and a nucleus as well as a contractile vacuole 

 was observed in each. The two daughter amoebae remained quiescent 

 and in contact for a few minutes, and at 11 o'clock were again active 

 and moving away. In some cases (fig. 20) the process was varied to 

 the following unimportant extent. The dividing myxamoeba (fig. 20a) 

 was extremely sluggish, and then elongated very slowly as in the 

 figure : two nuclei were now observed in it. This was at 1.17 o'clock. 

 Division then followed quickly, the nuclei not being noticed during 

 the process. The stage b was attained at 1.20, c at 1.22. The two 

 separated daughter amoebae remained quiescent for several minutes, 

 then slowly moved apart (d) to a very little distance, and then 

 encysted. Here again I have reasons for thinking that deficient 

 oxygen had to do with the sluggishness noticed in some cases. 



Encysted Stage. 2 

 As already stated, the myxamoeba? become dormant, round off into 

 a sphere, and form a delicate colourless membrane when oxygen is ' 

 deficient in the culture, or the temperature is very low, or from other 

 causes. This deficiency of oxygen may arise simplv from the fact that 

 the myxamcebEe have themselves increased so rapidly by division that 

 the supply of oxygen is unequal to their demand ; or it may be due 

 to other causes, among which the presence of Infusoria and other 



1 Cf. De Bary, Vergleichende Morphol. und Biol, der Pilze, &c, p. 455.— Zopf, Die Pilz- 

 Thiere, p. 10. 



2 Cf. De Bary, op. cit., p. 46, and Zopf, p« 90 



