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If, in the nearly allied families of the Ocypodidae and Grapsoidae, the closest agreement prevails in all the essential conditions of their structure; if the same plan of structure is slavishly followed in everything else, in the organs of sense, in the articulation of the limbs, in every trabecula and tuft of hairs in the complicated framework of the stomach, and in all the arrangements subserving aquatic respiration, even to the hairs of the flagella employed in cleaning the branchiae, why have we suddenly this exception, this complete difference, in connection with aerial respiration?
But the point of difficulty was B. termo. The demonstration of its flagella was a task of difficulty which only patient purpose could conquer.
There was no trace of an investing membrane; the constituent parts were related to each other simply as the two separating parts of an ordinary fission; and they now commenced a quick, writhing motion like a knot of eels, and then, in the course of from seven to thirty minutes, separated, and fully endowed with flagella swam freely away, minute but perfect forms, which by the rapid absorption of pabulum attained speedily to the parent size.
In the course of a few seconds there is no disconnected sarcode visible, and in five to seven minutes the organism is a union of two of the organisms, the swimming being again resumed, the flagella acting in apparent concert. This may continue for a short time, when movement begins to flag and then ceases.
Now you can see that I only have to lay this on the stage of a microscope, make it an object for a low power, and use a screw micrometer to find how many flagella go to the making of a body. The result is given in the figure; you see that ten flagella would fill the area occupied by the diameter of the body.
Yes! by a series of resolute efforts, in using a new battery of lenses the finest that at that time had ever been put into the hands of man I was enabled to show in succession that each motile form of Bacterium up to B. lineola accomplished its movements by fibers or flagella; and that in the act of self-division, constantly taking place, a new fiber was drawn out for each half before separation.
The fluid is lashed rhythmically by these fibers, and a spiral movement of the utmost grace results. Then do the intermediate forms that move also possess these flagella, and does this least form in nature, viz., Bacterium termo, accomplish its bounding and rebounding movements in the same way?
Nevertheless it may be remarked that in both species, especially in Ocypoda, the olfactory filaments in their ordinary situation are very much reduced, and when they are in the water their flagella never perform the peculiar beating movements which may be observed in other Crabs, and even in the larger Gelasimus; moreover, the organ of smell must probably be sought in these air-breathing Crabs, as in the air-breathing Vertebrata, at the entrance to the respiratory cavity.
The predominant organism is the bacillus of malignant œdema or vibrion septique of Pasteur, which is found in garden soil, dung, and various putrefying substances. It is anaërobic, and occurs as long, thick rods with somewhat rounded ends and several laterally placed flagella.
It consists of a large number of conical or pear-shaped individual cells, whose apices are turned toward the centre of the sphere. The cells are cemented together by a mucilaginous substance. Around their exposed larger ends, which form the surface of the sphere, are rows of flagella, by whose united action the colony rolls through the water.
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