December 1. 1899.] 



KNOWLEDGE 



271 



" The problem, where man first appeared on the earth and 

 from what form he sprang, has, m spite of all efforts of 

 modern geology and anthropology, up till now I'oimd no 

 solution " •? If we have indeed advanced, along the lines 

 indicated by the discovery of Dubois, it is but as yet a 

 single step, founded upon a single skeleton. To some 

 thinkers, however, this single step provides a field of 

 vision surpassing all that went before ; to others, the 

 coming of man remains, to this day, one of the profoundest 

 secrets of the crust. 



THE MYCETOZOA, AND SOME QUESTIONS 

 WHICH THEY SUGGEST.-VII. 



By the Right Hon. Sir Edw.uid Fry, d.c.l., ll.u., f.r.s., 

 and Agxes Fry. 



THEIR RELATIONS IN THE SWAEM SPORE 

 STAGE, — Reproduction by sicann tsiiates is by 

 no means conliued to the mysies. It plays a 

 conspicuous part in the cycle of Ufe in many of 

 the Algie and Fungi ; or rather we should say 

 conspicuous parts, for the functions of these simple pieces 

 of motile protoplasm are most various. Sometimes the 

 swarm spore is asexual and is of itself capable of repro- 

 ducing a new organism — as in some of the Algae and in the 

 Perowsporea, for instance, amongst the Fungi. In some 

 of the Alga? {Floriil ,r and Phaospored) the swarm cells 

 are sexual, and a conjugation between two of these moving 

 bodies occurs before the production of a new organism. 

 Sometimes the same organism (as in I'lra) produces two 

 kinds of swarm cells— the megaspores with four ciUa which 

 germinate asexually, and the microspores with two cilia 

 which germinate only upon conjugation. But more 

 remarkable still is perhaps the case of the well known and 

 beautiful Volvos — which appears to emit no less than four 

 distinct kinds of swarm spores, (1) sterile swarm spores ; 

 (2) asexual spores, or as they are called parthenospores-, (3) 

 male spores ; and (4) female spores. So marvellously 

 complicated are the modes in which Nature is capable of 

 differentiating and using to attain the same end by diflerent 

 roads that which seems the simplest thing in life — a 

 minute piece of naked protoplasm. 



In the swarm-spore state the myxies may thus seem to 

 claim relationship with the Algse and Fungi, but it is 

 doubtful whether much stress can be laid on this sugges- 

 tion, for (1) the existence of these cells as reproductive 

 spores is a wide- spread fact, and occurring in remote 

 groups of organisms, has perhaps but little value in 

 classification ; and (2) the mode in which mysies reproduce 

 through swarm spores is entirely different from that pursued 

 by any Alga or Fungus. It is, as we have already shown, 

 neither by parthenogenesis of the ordinary kind, nor by 

 conjugation, but by the fusion of a great number of swarm 

 spores, whether from the same or different sporangia, into 

 a single mass of plasmodium. 



But if we turn towards the animal kingdom, we shall 

 find that its claim to include the myxies in the swarm 

 spore stage is very strong. 



A mass of naked protoplasm, furnished with a nucleus 

 and vacuoles, capable of pushing forward pseudopodia, 

 and moving by these means, capable of including and 

 digesting food, and also of encystment — this is a descrip- 

 tion which will fit indifferently the swarm-spore of a mysie 

 and the weU-known Ama;ba, and we are thus brought to see 

 that close relationship, to which we have already referred, 

 between the swarm spores and the large group of protozoa 

 which naturalists generally place in the animal kingdom, 

 and all of which may be said to consist of undifferentiated 

 and naked protoplasm. 



Theib Relations in the Plasmodium Stage. — The motor 

 power of the plasmodium seems to recall animal life, but 

 we recollect that there are kindred organisms, like the 

 Diatoms, which are generally regarded as vegetable, and 

 retain a power of movement through hfe. 



As regards food, it is a familiar fact that, generaUy 

 speaking, plants feed on inorganic and animals on organic 

 substances. So far as observations have hitherto gone, 

 the food (if myxies consists of bacteria, or minute particles 

 of wood or faiigi (and, iu the case of Budhamin utricularh, 

 of living fungi). No evidence seems tn exist to shuw that 

 they have any power of deriving nutriment from inorganic 

 substances. The mode in which the mysies eject the 

 undigested matter recalls animal rather than vegetable 

 life. In the methods of digestion, therefore, they seem to 

 lean distinctly towards an animal character. 



The movement of the granules of protoplasm in the 

 Plasmodium is a phenomenon at least analogous to that 

 found in plants, and even iu plants with highly developed 

 cells, but it is not unknown amongst the lower forms 

 which are considered to be animals, for it appears t" have 

 been observed in some protista, and especially in the 

 tentacular-like pseudopodia. 



In the Plasmodium condition, the relationship of the 

 myxies seems on the whole rather with animals than 

 plants. 



Their Relations in the SpoRAJttiiuii Stage. — On the 

 other hand, when we reach the sporangium stage, the 

 absence of motion, the erect form, the stalk, the foot, the 

 spores, all recall some of the Fungi ; the elateis remind 

 us of the -Tungermanni*. 



The methods of opening the sporangia, sometimes by an 

 indefinite rupture, sometimes by a distinct operculum, 

 recall the distinction between the methods of opening 

 which prevail in the mosses. On the whole, the facies of 

 the sporangium stage is vegetable. 



One other observation which relates to all the stages of 

 development must be made. The two most characteristic 

 of vegetable compoimds are probably cellulose and 

 chlorophyll : though neither is found in aU plants, nor is 

 absent from some animals. Of chlorophyll we have no 

 trace in the myxies, and of cellulose very little. Nowhere 

 do we find it as the wall of a true and living cell as we do 

 in the most characteristic form of vegetable growth. 



Their Rel.ations REcoxsinEREu.^On the whole it seems 

 impossible to assign these minute organisms with any 

 certainty to the one realm or the other. If, with Haeckel, 

 we were, for purposes of classification, to speak of a new 

 kingdom— a buffer state between the animal and vegetable 

 realms, the Htgnuin pivtisticwn — we should no doubt 

 place the mysies there. But, if we retain the two ancient 

 kingdoms only, then it almost seems as if the mysies were 

 a vagrant tribe that wander sometimes on the one side, 

 and sometimes on the other side of the border line — 

 like nomads wandering across the frontier of two settled 

 and adjoining States, to neither of which they belong. 

 They would seem to begin life as animals and end it as 

 vegetables — a life-history not without some sad analogies 

 in human experience. 



The absence of a satisfactory position for the myxies in 

 the great network of organized beings leads one to think 

 of them as a group which probably from very remote 

 antiquity has stood aside from the great currents of 

 evolution, whether in the animal or the vegetable world. 



Distribution. — The species at present known of mysies 

 are not very numerous. Mr. Lister figures less than two 

 hundred in his monograph ; De Bary speaks of them as 

 numbering nearly three hundred. No doubt many species 

 remain to be discovered. 



