Januaby 2, 1899.] 



KNOWLEDGE. 



and become covered with a hard coating, and in that 

 condition are known as Microctjsts. But from the wall of 

 this cyst the contents afterwards escape, and renew their 

 movements. 



The swarm spores (whether after encystment or not) now 

 enter upon a new stage. They gather together and fuse 

 into masses of naked protoplasm, the swarm spores 

 losing their individuality in a common mass. This mass 

 is called a Plasmodium. This plasmodium grows in bulk 

 by the digestion of food, such as bits of fungus or dead 

 wood, and attracts to, and unites with itself, other 

 smaller plasmodia of the same species. In the Badhamia 

 utricularis this plasmodium is yellow ; it is white in many 

 species ; green or orange, or red or grey in other kinds. 

 This Plasmodium moves, sometimes through the substances 

 of dead wood, in other cases on the surface, expanding in 

 an irregular fan shape, and marked irregularly by streaks 

 or veins, as may be seen in Fig. 4. It appears to move in 



(?^" 



^^ 



•^ 



Fio. -t.- 



■Streaming plasmodium of Didymium leucopus. 

 (After Cienkowski.) 



search of its requisite food. The Badhamia is much 

 devoted to fungi, and will extend itself over the surface of 

 a fungus till it has devoured all its more delicate parts. 



In the substance of this plasmodium there arises a strong 

 alternate movement of the more fluid protoplasm, a rush 

 of circulation through the channels of the plasmodium. 

 The granules move for a short time in the one direction, 

 then pause, and then move in the opposite way. The 

 strongest currents are indicated in Fig. i by the letters st. 



The Plasmodia of different species differ much as regards 

 size. In some genera they are very visible, and were 

 known to some of the older botanists as Mesenteric, and 

 were believed to be a species of fungus. In some cases 

 they can only be discovered by the microscope ; and, 

 haunting the interstices of dead wood, they are rarely 

 visible. Such are the plasmodia of Lycogala, Arcyria, and 

 of some species of Trichia. 



Here, again, a phenomenon of encystment sometimes 

 occurs. During drought the plasmodium may become 

 quite dry and hard without losing vitality. In this stage 

 the hard plasmodium bears the name oi scleiotium. That 

 of the Badhamia is quite horny, and orange-red in colour. 

 On being wetted it will resume its old plasmodium form, 

 and move as before. 



This conversion from an active into a passive condition 

 of the Plasmodium seems to be brought about by two con- 



ditions — the want of moisture and the want of food. This 

 last fact is illustrated by a case in which a plasmodium 

 placed on wet cotton wool, but without food, was found to 

 turn into a sclerotium. The capacity for rest and awaken- 

 ing is thus a protective one, and enables the organism to 

 tide over a time of famine or drought. It is certainly a 

 better plan even than the Lydian practice of playing games 

 to forget hunger. 



From the plasmodium stage, whether broken into by a 

 sclerotium condition or not, the organism, after a time, 

 prepares for its next effort. It seeks some spot, on the 

 surface of dead wood or leaves, sometimes a rather exposed 

 and elevated position, at other times a sheltered one, and 

 there forms sporangia, so that what before was a mass of 

 more or less amorphous protoplasm has differentiated itself 

 into several parts, into delicate pedicels, the coating mem- 

 brane of the sporangia, the hairs of the capillitium, and the 

 spores — which in due time are to begin again the circuit 

 of the life-history of the Badhamia, which is in all essen- 

 tial features that of the whole group of myxies. The 

 sporangia in the course of their development sometimes 

 undergo a great change in colour ; for instance, the young 

 sporangia of Comatricha are an ivory white, and they 

 gradually change into a glossy black ; and the gi-oups of 

 little tree-like growths with their developing forms and 

 varying colours, all gathered together within a few square 

 inches, is a sight of great beauty. In the maturity of this 

 sporangium stage of the organism it has lost all its powers 

 of locomotion, it has lost its powers for digestion, and in 

 its stationary condition devotes its energies to the 

 reproduction of the species. The motion of the granules 

 of the protoplasm continues to some extent until the forma- 

 tion of the spores. 



Now, pausing here for a moment, and taking merely the 

 outline of the facts as we have drawn it, we have surely 

 abundance of matter for thought and surprise. Some 

 seventy years ago. Fries, one of the first naturalists who 

 grasped the series of changes through which these organisms 

 pass, compared these changes to the metamorphoses of 

 insects. We get, too, an inkling of the difficulty which 

 naturalists have felt in assigning the myxies either to the 

 animal or the vegetable kingdom : their locomotion and 

 rapacious youth seem to shut them out from the plants ; 

 their stationary condition and their production of sporangia 

 from the animal world. 



The life-history of our organism may be briefly 

 summarized in the following diagram, in which the circle 



J*!/! 



i;mO(iuco^ 







\ 



tp 



shows the essential stages of Ufe, and the ontliers show 

 occasional and non-essential stages. 



We wish to dwell a little more on some of the points of 



