12 



PROTOZOA 



spores (one corresponding to each nucleus of the enclosed plas- 

 modium) each of which has a cellulose coat, and (b) a capillitium 

 of threads which hold the spores together. Each spore (chlamydo- 

 spore) liberates on germination a single mieleated flagellula, which 

 develops into an amcebula, which in turn fuses with other amcebulie 

 to form the plasmodium. The Endosporea are essentially dwellers 

 on rotten wood and such vegetable refuse. 



FIG. III. Mycetozoa (after DeBary). 1-6. Germination of spore(l) of Trichta 

 varia, showing the emerging "flagellula" (4, 5), and its conversion into an 

 "amcebula" (6). 7-18. Series leadintr from spore to plasmodium phase of 

 Chondrioderma difforme: 7, spore; 10, flagellula; 1'2, amcebula; 14, apposi- 

 tion of two amcebulaB ; 15-17, fusions ; 18, plasmodium. 19, 20, Spore-fruit 

 (cyst) of Ptiysarum JcueopfuEum, Fr. (x 25), the former from the surface, the 

 latter in section with the spores removed to show the sustentacular network or 

 capillitium. 21. Section of the spore-cyst of Didymium squaintilosum,viith the 

 spores removed to show the radiating capillitium x and the stalk. 



Sub-order 1. PERITHICHEA, Zopf. 



Fain. 1. CLATHROPTYCHIACEJE, Rostafinski. 



Genera. Clathroptyckium, Rost. ; Enteridium, Ehr. 

 Fam. 2. CniBRARiACE^;. 



Genera. Dictydium, Pers. ; Cribraria, Pers. 



Sub-order 2. EXDOTRICHEA, Zopf. 



Fam. 1. PHYSAREA. 



Genera. Physarum, Pers.; Craterium, Trentepol; Eadliamia, 

 Berkeley ; Leocarpiis, Link. ; Tilmadochc, Fr. ; Fuligo 

 (slSthalium), Hall ; ^Ethaliopsis, Z. 

 Fam. 2. DIDYMIACE.E. 



Genera. Didymium; Lepidodcrma, DeBary. 

 Fam. 3. SpUMAKIACEai. 



Genera. Spuniaria, Pers. ; Diachca, Fries. 

 Fam. 4. STEMONITEA. 



Genera. Stemonitis, Gleditsch ; Comatricfta, Preuss ; Lam- 



prodcrma, Rost. 

 Fam. 5. ENERTHKNEMEA. 



Genera. Enerthema, Bowman. 

 Fam. 6. RETICULARIACE.E, Zopf. 



Genera. Amauroch&te, Rost; Selwularia, Bull. 

 Fam. 7. TRICHINACE^;. 



Genera. ffemiarcyria, Rost. ; Trichia, Hall. 

 Fam. 8. ARCYRIACEJE. 



Genera. Arcyria, Hall; Cornuvia, Rost.; Lycor/ala, Ehr. 

 Fam. 9. PERicH^NACEi;. 



Genera. Perich&na, Fries. ; Lachnobolus, Fries. 

 Fam. 10. LICEACE^E. 



Genera. Licca, Schrader ; Tiibulina, Pers.: Lindbladia, 

 Fries. ; TubuUfcra, Zopf. 



ORDER 3. EXOSPOREA, Zopf. 



Characters. The chlamydospore liberates an amcebula iu the 

 first instance, which develops into a flagellula. This subsequently 

 returns to the amceba form, and by fusion with other amxBbulse it 

 forms a true fusion plasmodium. The spores are not produced 

 within a cyst but upon the surface of column-like up-growths of the 

 plasmodium, each spore (conidum) forming as a little spherical out- 

 growth attached to the column (conidiophor) by a distinct pedicle. 



Sole Genus. Ceratium, [This name must be changed, since it 

 was already applied to a genus of Dinoflagellata, when Famintziu 

 and Worouin gave it to this Mycetozoon.] 



Further Remarks on Mycetozoa. About two hundred species of 

 Mycetozoa have been described. Botanists, and especially those who 

 occupy themselves with Fungi, have accumulated the very large 



mass of facts now known in reference to these organisms ; never- 

 theless the most eminent botanist who has clone more than any 

 other to advance our knowledge of Myeetozoa, namely, De Bary, has 

 expressed the view that they are to be regarded rather as animals 

 than as plants. The fact is that, once the question is raised, it 

 becomes as reasonable to relegate all the Gymnomyxa without 

 exception to the vegetable kingdom as to do so with the Mycetozoa. 

 Whatever course we take with the latter, we must take also with 

 the Heliozoa, the Radiolaria, and the Reticularia. 



The formation of plasmodia, for which the Mycetozoa are conspicu- 

 ous, appears to be a particular instance of the general phenomenon 

 of cell-conjugation. Small plasmodia are formed by some of the 

 Proteomyxa ; but among the other Gymnomyxa, excepting Myceto- 

 zoa, and among Corticate Protozoa, the fusion of two individuals 

 (conjugation scum stricto) is more usual than the fusion of several. 

 Zopf (13) has attempted to distinguish arbitrarily between conjuga- 

 tion and plasmodium formation by asserting that in the former 

 the nuclei of the cells which fuse are also fused, whereas in the 

 latter process the nuclei retain their independence. Both state- 

 ments are questionable. What happens to the nucleus in such 

 conjugations as those of the Gregarinre has not yet been made out, 

 whilst it is only quite recently that Strasburger (30) has shown 

 that the plasmodia of Mycetozoa contain numerous scattered nuclei, 

 and it is not known that fusion does not occur between some of 

 these. There is no doubt that the nuclei of plasmodia multiply 

 by fission, though we have no detailed account of the process. 



The Sorophora are exceptional in that the amoeba? which unite to 

 form a cell-colony iu their case do not actually fuse but only remain 

 in close contact ; with this goes the fact that there are no large 

 spore-cysts, but an identification of spore and spore-cyst. The 

 amcebie arrange themselves in stalked clusters (sori), and each be- 

 comes encysted : one may, in this case, consider the cyst equally as 

 a spore or as a spore-cyst which produces but a single spore. The 

 amceba; described by various writers as inhabiting the alimentary 

 canal and the dung of higher animals (including man) belong to 

 this group. The form described by Cunningham in the Quart. 

 Jour. Micr. Sci., 1881, as Protomyxomyces coprinarius is appa- 

 rently related to the Copromyxa (Gitttulina) protca of Fayod (31). 



The spore-fruits of the Endosporese occur in various degrees of 

 elaboration. Usually they are (1) spherical or pear-shaped cysts 

 with or without an obvious stalk (Fig. III. 19, 20, 21), and often 

 have a brilliant colour, and are of a size readily observed by the 

 naked eye, the plasmodia which give rise to them being by no 

 means microscopic. But they may present themselves (2) as 

 irregular ridges growing up from the plasmodium, when they are 

 termed serpula forms. Lastly, the cysts may be united side by 

 side in larger or smaller groups instead of forming at various sepa- 

 rate points of the plasmodium. These composite bodies are termed 

 "fruit-cakes" or sthalia," in view of the fact that the spore-cysts 

 of Fuligo, also called jEthalium the well-known "flowers of tan" 

 form a cake of this description. 



The capillitium or network of threads which lies between the 

 spores in the spore-cysts of Endosporeie is a remarkable structure 

 which exhibits special elaborations in detail in different genera, here 

 not to be noticed for want of space. Although definite in form and 

 structure, these threads are not built up by cells but are formed 

 by a residual protoplasm (cf. Sporozoa) which is left in the cyst 

 after the spores have been segregated and enclosed each in its 

 special coat. They are often impregnated by calcium carbonate, 

 and exhibit crystalline masses of it, as does also the cyst-wall. 



The spores of the Mycetozoa are as a rule about the T-sVoth inch 

 in diameter. They are produced by millions in the large fruit- 

 cakes of such forms as Fuligo. Often the spore-coat is coloured ; it 

 always consists of a substance which gives the cellulose reaction 

 with iodine and sulphuric acid. This has been sometimes con- 

 sidered an indication of the vegetable nature of the Mycetozoa, but 

 cannot be so regarded since many animals (especially the Tunieata 

 and various Protozoa) produce substances giving this same reaction. 



Dryness, low temperature, and want of nutriment lead to a dor- 

 mant condition of the protoplasm of the plasmodium of many 

 Mycetozoa and to its enclosure in cyst-like growths known as 

 "sclerotia," which do not give rise to spores, but from which the 

 protoplasm creeps forth unaltered when temperature, nutrition, and 

 moisture are again favourable. The sclerotia are similar in nature 

 to the hypnocysts of other Protozoa. 



The physiological properties chemical composition, digestive 

 action, reaction to moisture, heat, light, and other physical influ- 

 ences of the plasmodia of Mycetozoa have been made the subject 

 of important investigations ; they furnish the largest masses of 

 undirTerentiated protoplasm available for such study. The reader 

 is referred to Zopf's admirable treatise (13) as to these matters, and 

 also for a detailed account of the genera and species. 



CLASS III. LOBOSA, Carpenter. 



Characters. Gymnomyxa in which (as in the succeeding four 

 classes) the amoeba-phase predominates over the others iu perma- 

 nence, size attained, and physiological importance. The pseudo- 



