. The microscope and its revelations. be due, not to the growth of thethread, but to osmotic changes in the cell-contents. He regards themas being of the same nature as the movements of the sarcode in thepseudopodia of rhizopods and other protozoa. Schnetzler 4 describesthe movements in Oscillatoi i« as of six different kinds : (1) rotation ofthe thread or of its segments round its axis ; (2) creeping or gliding-over a solid substratum ; (3) a free-swimming movement in the water :(4) Iotation or flexion of the entire thread ; (5) sharp tremblings or concussions ; and (6) a radiating arrange-me
. The microscope and its revelations. be due, not to the growth of thethread, but to osmotic changes in the cell-contents. He regards themas being of the same nature as the movements of the sarcode in thepseudopodia of rhizopods and other protozoa. Schnetzler 4 describesthe movements in Oscillatoi i« as of six different kinds : (1) rotation ofthe thread or of its segments round its axis ; (2) creeping or gliding-over a solid substratum ; (3) a free-swimming movement in the water :(4) Iotation or flexion of the entire thread ; (5) sharp tremblings or concussions ; and (6) a radiating arrange-ment of the entangled threads. Themovements are greatly influenced bytemperature and light, being much moreactive in warmth and sunshine than incold and shade. There are no zoosporesproduced, nor is any sexual mode ofgeneration known. The Rivulariaceceand Scytonemacece (Pis. YII and VIII)are exceedingly common organisms instagnant water, resembling the Oscilla-toriacete in their blue-green colour, andin their reproduction by means of. hormogoiies. PIG. 419.—Poitioii of gelatinousfrond of Nostoc. Nearly allied to the preceding is thefamily of Nostocacece, consisting ofdistinctly beaded filaments, which, inthe most familiar genus, Nostoc, lie infirmly gelatinous envelopes of definiteoutline (fig. 419). The filaments areusually simple, though sometimes denselyinterwoven, and arc almost always curvedor twisted, often ta king a spiral direction. The masses of jelly in which they are imbedded are sometimesglobular or nearly so, and sometimes extend in more or lessregular branches; they frequently attain a very considerablesize ; and as they occasionally present themselves quite suddenly(especially in the latter part of autumn on damp garden-walks),they have received the name of fallen stars. They are notalways so suddenly produced, Imuever. as they appear to lie: forthey shrink up into mere films in dry weather and expand againwith the first, shower. Other species are not unfrequenl
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
