United States or Falkland Islands ? Vote for the TOP Country of the Week !
Finally, in colonial forms, most of the cells in the colony ceased to have any share in reproduction, that function being relegated to the activities of a few cells which broke away and united with others similarly adrift. These cells functioning for reproduction continued to differentiate more and more, until large ova and small, motile spermtozoa were definitely developed.
The wind is dropping this evening, and I have been up to Wind Vane Hill. I now think the ice has remained fast. There has been astonishingly little drift with the wind, probably due to the fact that there has been so very little snowfall of late. Atkinson is pretty certain that he has isolated a very motile bacterium in the snow.
If some drops of septic serum be spread horizontally in a tube and in a very thin layer, the fluid will become absolutely harmless in less than half a day, even if at first it was so virulent as to produce death upon the inoculation of the smallest portion of a drop. Furthermore all the vibrios, which crowded the liquid as motile threads, are destroyed and disappear.
He proceeded to draw divisions between the bottom organisms without power of motion, benthon, the nekton motile life in mid-water, and the plankton or floating life. Then he led very prettily on to the importance of the tiny vegetable organisms as the basis of all life.
"To be specific," Retief said, "there'll be 50,000 Tatone B-3 dry washers; 100,000 Glo-float motile lamps; 100,000 Earthworm Minor garden cultivators; 25,000 Veco space heaters; and 75,000 replacement elements for Ford Monomeg drives." "Like I said. A lot of junk." Retief leaned back, looking sardonically at Zorn, "Here's the gimmick, Zorn," he said.
If the period of sexual excitement extends over fifteen to thirty minutes, the whole duct system from the epididymis to the ampulla becomes gorged with the secreted testicular product. This secretion consists of active motile spermatozoa, of spermatic granules and of mucus.
Some multiply by fission, others by sporulation. Some forms are motile, others are non-motile. Tuberculosis, tetanus, anthrax, and many other surgical diseases are due to different forms of bacilli. Spirilla are long, slender, thread-like cells, more or less spiral or wavy. Some move by a screw-like contraction of the protoplasm, some by flagellæ.
The motile force is imparted to the gonidium by dense rows of waving cilia with which it is completely surrounded. Owing to their rapid vibration, it is almost impossible to distinguish them while the spore is in active motion, but their effect is very plainly seen on adding colored pigment particles to the water.
The chromatin of the nucleus contains the determinants of hereditary qualities. In reproduction, the male sex-cell, which is scarcely more than a minute mass of chromatin provided with a thin coat of protoplasm and a motile organ, fuses with the egg, and the nuclei of the two cells unite to form a double body, which contains equal contributions of chromatin from the two parental organisms.
In short, the bacteria after two centuries of study appear to us about as they did at first. They must still be described as minute spheres, rods, or spirals, with no further discernible structure, sometimes motile and sometimes stationary, sometimes producing spores and sometimes not, and multiplying universally by binary fission.
Word Of The Day