NEW VIEW OF THE MECHANISM OF RESPIRATION 



303 



" The length of time during which the plasmodium will continue to feed and increase in bulk before changing 

 into sporangia difiers according to the species, and also to the conditions of its surroundings. Physarum psit- 

 tacinum, which inhabits the rotten stumps of old trees, appears to pass twelve months in the plasmodium stage ; 

 on the other hand, Didymium difforme will go through the several stages from germination of the spores to the 

 formation of the sporangia in a fortnight. 



" The Plasmodium, if allowed to dry, passes into the sclerotium or resting stage (Fig. 59, A). The sclerotium 

 of Badhamia utricularis is dull orange-red in colour, of horny consistence, and made up of a multitude of thin-walled 

 cysts closely packed together ; each cyst being filled with granular protoplasm, among which ten to twenty nuclei 

 are interspersed. On being wetted the sclerotium will revive in the course of a few hours and resume the streaming 

 movement. Preserved in a dry state, it will retain its vitality for three or four years, but it is longer in reviving 

 according to the length of time it has remained in the resting condition. 



" Carbonate of Ume is usually abundant in the plasmodium and young sporangia of the species comprised in 

 the sub-cohort Galcarineie. In most genera of the order Physaracea?. these granules are withdrawn from the plasma 

 before the spores are formed, and are deposited partly in the sporangium-wall, 

 and partly in vesicular expansions of the capillitium. These expansions take 

 various shapes : they are globose, fusiform, or branched, and are sometimes fused 

 together in the centre of the sporangium, forming a pseudo-columella. In the 

 descriptions of the species they are termed lime-knots. In the Didymiacem the 

 granules in the yoimg sporangia are dissolved at a certain stage, and the salt 

 forms again in crystals on the outside of the wall. 



" The sub-class Exospore^ is represented by the single genus Ceratiomyxa 

 (Fig. 60, A to H), and is characterised by the numerous white spores being borne 

 on the outside of columnar or branching sporophores. These are delicate, fragile 

 structures, often covering two or three square inches of the dead wood on which 

 they grow. The surface of the sporophore is mapped out into polyhedral areolae, 

 from the centre of each of which arises a slender stalk bearing a single ellipsoid 

 spore. On placing the ripe spores in water, the membranous spore-wall at once 

 shps ofi, and the naked contents he for several hours without apparent change, 

 retaining their elhpsoid form. A constriction then takes place at right angles 

 to the long axis, and before division is completed a second constriction of each 

 half occurs ; each of the four lobes thus formed again becomes constricted, and 

 we have eight globular bodies adhering together and exhibiting slow amoeboid 

 movement ; each of these bodies now produces a flagellum, and the cluster swims 

 away by the aid of the lashing flagella. 



" Experiment shows that, whatever may be the digestive principle of plasmodium (possibly a peptonising 

 ferment, as suggested by Krukenberg), it is not confined to any special part of the mass. With starch and the 

 sections of agarics the absorption took place in the streaming interior, while in the case last related it occurred in 

 the hyaloplasm alone ; the threads were completely dissolved in the hyaline margin, with the exception of the 

 small fragments referred to, which were kept under constant observation until they were almost ejected by the 

 far-retreating plasmodium." ^ 



The movements of Badhamia utricularis, especially the advancing movements, afiord a striking example of the 

 aggressive nature of life. Living plants and animals continually and habitually project themselves against objects 

 which they incorporate and ultimately assimilate ; a due selection of objects being in every case made. The 

 objects approached, incorporated, and assimilated, being for the most part dead, cannot assume an active role. 

 It is, in every instance, the prerogative of the living thing to advance, and it does so, in all cases, as an invader. The 

 Plasmodium of Badhamia advances, and in so doing it exerts what is virtually a pushing, elongating, dilating, and 

 centrifugal power : it also recedes, and when faUing back it pulls itself together and exerts a pulhng, shortening, 

 contracting, and centripetal power. These two movements, which are complemental, are fundamental and indis- 

 pensable in all living things. They occur in the substance of the amoeba, in pseudopodia, and in the voluntary and 

 involuntary muscles ; these substances being invested, as I long ago explained,^ with the double power of elongating 

 and shortening, and being very largely concerned in seizing and dismissing food and other materials in the economy 

 of the individual ; they occur in the respiratory, circulatory, and other rhythmic movements, of which they form 



'■ "Notea on the Plasmodium of Badhamia utricularis and Brefeldia jiiaxlmn. Guide to the British Mycetozoa." London, 1895. See 

 also Annals of Botany for June 1888. 



^ " On the Physiology of the Circulation in Plants, in the Lower Animals, and in Man," from pages 184 to 243 inclusive. Macmillau & Co., 

 London, 1874 ; originally published in the Edinburgh Medical Journal in 1872. 



Fig. 60. — Ceratiomyxa mucida 

 (Schroet). A. Spore. B. Spore-contents 

 escaping from the spore-wall. C to G. 

 Successive stages in the division of the 

 naked spore into eight. H. Cluster of 

 eight swarm-cells. Magnified 900 times. 



