AN AQUATIC MYXOMTCETE. 83 



instead of gliding over the surface stuck to it and were either at once 

 drawn in, as it were, or partially separated off and then again became 

 part of the larger mass. In some cultures I had as many as eight or 

 nine separate plasmodia slowly moving on the glass for two or three 

 days. 



One of the largest (more than a millimeter in length) is drawn at 

 fig. 26, and a description of it will serve once for all. Its changing 

 outlines were very irregular : short and long pseudopodia would be 

 put forth together or separately, and withdrawn or extended, the fine 

 granules (as well as fewer larger ones and nuclei) flowing quickly 

 down the central portion. The general hue was a pale dirty yellow, 

 the very clear ectoplasm being colourless, in thin parts at any rate. 

 There were several or even many contractile vacuoles varying in size 

 and activity. Bacteria, spores, empty cysts and other objects were 

 frequently observed in the plasmodium, and were also seen to be en- 

 veloped by its pseudopodia ; some to be earned into the interior, others 

 to become free again as the pseudopodia withdrew. The following 

 curious phenomenon was observed more than once. The actively 

 moving plasmodium would come to rest in irregular or rounded clumps 

 during the night (fig. 27), possibly on account of the lowered tempera- 

 ture, and would then spread out again next morning, and move as 

 before : this would be repeated — even several times. In other cases 

 this dormant condition would last a longer time, and a distinct invest- 

 ment (the character of which was not made out exactly) would be 

 excreted (fig. 27a and b) suggesting an effort on the part of the plasmo- 

 dium to produce a sporangium. 1 No undoubted sporangia were formed 

 in the suspended drops, however. 



There can be little doubt that external conditions have to do with 

 these changes ; but although I have notes on the subject which show 

 that at certain stages the myxamcebee collect at the lighted side or on 

 the free surface of the drop, while at others they choose the surface 

 of the glass generally, and that the plasmodia seem to favour the 

 upper regions of the drop, they are too scanty and not sufficiently 

 decisive for the purpose of determining the questions which arise. 



The failure to produce sporangia in the above cultures, and the 

 observation that the plasmodia tend to the upper regions of the drop, 

 however, led me to try the following experiment, which was at any 



1 Or they may be the " macro-cysts " described by Cienkowski in Pericfioenia.—CL Zopf, 

 p 92. 



