PROTOCOCCUS. 



[ 640 ] 



PROIOMYCES. 



form appear to consist partly of oil-glo- 

 bules ; in the green form the protoplasmic 

 substance is coloured by chlorophyll; and at 

 a certain stage contains starch. 



We have traced P. viridis through all 

 these stages, as represented in PI. 7. fig. 

 2 a-y : a most elaborate monograph of P. 

 pluvialis by Cohn goes to establish the same 

 conclusion, that the genus Hcematococcus is 

 founded on states of Protococcus. The P. 

 viridis of our figures is undoubtedly Clila- 

 midomonas, synonymous with Diselmis, Du- 

 jardin. This form appears at first sight 

 nearly allied to Euglena-, but there are 

 striking differences in the appearance and 

 movements of the active forms, and the 

 vegetative forms are somewhat different. 

 It may be remarked, however, that the 

 zoospores of Protococcus viridis, allowed to 

 dry upon a slide, often turn red and look 

 just like small Astasice (PI. 7. fig. 2#). 



We have remarked under PALMELLA, 

 that the Polar red snow appears to be a 

 Palmella (PI. 7. fig. 3d), although this 

 species has been called Protococcus and 

 Hcematococcus nivalis ; and it appears to us 

 that Shuttleworth and others have con- 

 founded this with Protococcus pluvialis. 

 Hassall's species of Hcematococcus, nos. 8 to 

 19, with the exception of H. vulyaris (Chlo- 

 rococcum) (PI. 7. fig. 1), are probably con- 

 generic with our P. viridis. 



Our P. viridis makes its appearance com- 

 monly on damp earth, sand, &c., forming a 

 greenish coat of no perceptible thickness; 

 and the zoospores (Chlamidomonas) occur 

 constantly in standing pools in spring and 

 autumn, tinging the surface of the water 

 bright green, and, as they settle to rest, 

 forming a kind of green scum at the mar- 

 gins, constituting the green matter of 

 Priestley. Cells of resting-fonn 1-2400" 

 in diameter. P. pluvialis colours water red 

 in like manner ; it occurs on mountains, 

 especially in melted snow-water. Cells of 

 reating-form 1-1250 to 1-625" in diameter. 

 Similar colorations, however, are produced 

 by various other organisms (see WATER}. 



It may be observed that when the active 

 forms of P. viridis and P. pluvialis divide 

 without coming to rest, they produce forms 

 which are undistinguishable from many of 

 Ehrenberg's species of Polygastrica. When 

 they acquire a loose cellulose coat before 

 losing their cilia, they represent Gyges ; at 

 other times they resemble Chlorogonium, 

 Uvella, Polytoma, Monas, Bodo, &c. 



BIBL. Harvey, Br. Alg. 1. 180 ; Hassall, 



Fr. Ala. 321 ; Meneghini, Tr. Turin Ac. 2. 

 v. 1 ; Cohn, Nova Acta, xxii. 605, Ray Soc. 

 1853, 514; Von Flotow, Nova Acta, xx. 

 414; Braun, Verjunyuny, Ray Soc. 1853, 

 206 ; Nageli, Einzelliye Algen ; Kiitzing, Sp. 

 Alg. 196 ; Tab. Phyc. i. ; Rabenh. Alg. iii. 

 56 ; Cooke, Fr. ivat. Algce, 1882. See also 

 RED SNOW. 



PROTODER'MA, Ktz. A genus of Ul- 

 vacese (Confervoid Algae). 



Char. Cells forming a thin ineinbrano- 

 crustaceous expansion ; they are roundish 

 angular. P. viride (PL 3. fig. 18), fresh- 

 water; on stones; cells 1-300". 



BIBL. Ktz. Phyc. Gen. 295 ; Rabenht. 

 Alg. iii. 307. 



PROTOG'ENES, Haeckel. A genus of 

 Protista. 



Char. A simple shameless protoplasm body 

 without vacuoles, which protrudes ramify- 

 ing and anastomosing processes, and repro- 

 duces itself by fission. Protogenes primor- 

 dialis. Body sometimes globular,from 1-200- 

 1-25" diameter, sometimes extended and 

 flattened out, with irregular outline, to 1-10" 

 diameter; pseudopodia exceedingly nume- 

 rous, over a thousand, very fine, with very 

 numerous ramifications and anastomoses. 

 Mediterranean. 



BIBL. Haeckel, Zeitschr. iviss. Zool. xv. 

 1865, 360. 



PROTOHY'DRA, Greef. A genus of 

 Zoophytes. Like Hydra', but simpler in 

 structure, as it has no tentacles. Reproduc- 

 tion by transverse fission ; nematophores and 

 pigment-cells present. 



BIBL. Greef, Sieb. u. Kdll. Zeit. i. 1870; 

 Qu. Mic. Jn. 1870, 297. 



PROTOM'ONAS, Haeckel. A genus of 

 Protista. 



Char. A simple protoplast, without 

 vacuoles, simple or ramifying pseudopodia. 

 Reproduction by zoospores, which combine 

 into meshes or plasmodia. 



Protomonas amyli. In decaying Nitella. 

 (Haeckel, Gen. Morph. vol. ii. 23, Qu. Mic. 

 Jn. 1869.) 



PROTOM'YCES, linger. A genus of 

 Fungi, the affinities of which are very 

 doubtful ; placed in Ascomycetes by Sachs, 

 but apparently forming a degraded branch 

 of Phycomycetes. They grow in the inter- 

 cellular passages of leaves and leaf-stalks. 

 According to De Bary, these Fungi consist 

 of ramified filaments creeping between the 

 cells of soft tissues, and swelling up at inter- 

 vals (apparently where they meet an inter- 

 cellular space large enough), to form globular 



