842 SUMMARY OF CURRENT RESEARCHES RELATING TO 



small; endochrome pale red; membrane delicate, coloured blue by 

 iodine and sulphuric acid. Endochrome escapes simultaneously in 

 two or three portions ; the division taking place before the com- 

 mencement of the escape. Zoospores very small, of irregular amoeboid 

 appearance, with only a few short pointed pseudopodia. In conjugating 

 the zoospores envelope the isolated cells of the host (unicellular algse), 

 forming a new cyst round them, or several individuals are thus 

 enveloped. Eesting cysts unknown. 



3. Monas Cnk. (only 1 species, Monas amyli, or Protomonas 

 Haeck.). Cysts spherical, with simple thin membrane and colourless 

 endochrome, from which a number of zoospores are formed. Zoospores, 

 at first fusiform and bi-ciliated, with serpentine motion, after- 

 wards amoeboid or actinophrys-like, with several fine pointed pseu- 

 dopodia and slow movements, during which they change their form. 

 Small plasmodia formed from the coalescence of several amoeboid 

 zoospores. The hosts (grains of starch) are surrounded by the 

 zoospores or plasmodia, thus forming a new cyst ; several zoospores 

 often coalesce on the same starch-grain. Eesting cysts formed by 

 the ordinary cysts throwing off the unconsumed nutrient material, 

 and enveloping themselves with a new membrane, wart-like projec- 

 tions appearing on the inner side of the original membrane. 



4. Protomyxa Haeck. (only 1 species, P. aurantiaca). Cysts 

 spherical, with moderately thick membrane, structureless, and not 

 coloured blue by iodine and sulphuric acid. The fine-grained orange- 

 red endochrome breaks up into a number of portions, each of which 

 escapes as a zoospore. Zoospores pear-shaped, with a single cilium 

 at the narrow end, and slow motion, subsequently amoeboid and 

 protean. Large plasmodia formed by the coalescence of several 

 amoeboid zoospores, furnished with branched anastomosing pseu- 

 dopodia and vacuoles. The hosts (various diatoms) are surrounded 

 by the amoeboid zoospores or plasmodia, and their shells thrown out 

 after their contents have been absorbed ; a new cyst is thus formed, 

 a new membrane being excreted. Eesting cysts unknown. 



MICEOSCOPY. 

 o. Instruments, Accessories, &c. 



Petrograpbical, Mineralogical, or Lithological Microscopes — 

 Rosenbusch, Fuess, Beck, Swift, &c. — (1) Bosenbusch's Petrographical 

 Microscope. — Special Microscopes for the examination of minerals and 

 rocks are now supplied by nearly every optician. The original of 

 such instruments * is the one devised by Professor Eosenbusch, in 

 1876,| which is illustrated in Fig. 150, with a few modifications 

 introduced in its manufacture by E. Fuess, of Berlin.]: 



* A "Mineralogical Microscope" was described by S. Highley in Quart. 

 Journ. Micr. Sri., iv. (1856) pp. 281-6 (3 figs.). 



t Neues Jabrbucb f. Mineral., 1876, p. 504. 



% Cf. Loewenberz, L., ' Bericbt iiber die Wiss. Instrumente auf der Berliner 

 Gewerbeausstellung im Jabre 1879,' pp. 282-6 (1 fig.), pp. 350-3 (1 fig). 



