Page:Popular Science Monthly Volume 50.djvu/737

Rh present views, however, we can hardly suppose that organisms acquired hard parts at a very early period of their existence, and fauna after fauna may have occupied the globe and disappeared, leaving no trace of their having lived. In such case we are not likely ever to obtain from fossils definite knowledge of the character of the earliest faunas; and the biologist must not look to the geologist for direct information concerning the dawn of life upon the earth. The importance of detailed work may be inferred from a consideration of the great increase of our knowledge of the Permo-Carboniferous faunas as the result of recent labors in remote regions. It is specially desirable that the ancient faunas and floras of tropical regions should be more fully made known, as a study of these will probably throw considerable light upon the influence of climate on the geographical distribution of organisms in past times.

A Lobster's Motions.—The adult lobster, as appears from Dr. F. H. Herrick's study in the Bulletin of the United States Fish Commission, lives and feeds exclusively upon the sea bottom, which it never leaves of its own accord in any considerable degree. In traveling over the bottom in search of its prey, the lobster walks nimbly upon the tips of its slender legs. The large claws are extended in front of the head, a position which offers the least resistance to the water, while the two hinder pairs of walking legs, which end in hard, spurlike joints, serve as picks to steady the movements of the animal. In thus getting about, it has the constant aid of the delicate swimmerets, attached vertically to the under surface of the "tail," each of which consists of a short stalk and two very flexible blades. By the movements of the swimmerets the lobster is impelled slowly forward without the aid of the walking legs. The branches of the swimming feet are garnished with long, chitinous setœ or hairs, to which the eggs of the female are attached. When taken out of the water the lobster can only crawl in its vain attempts to walk, owing to the heavy body and claws, which the slender walking legs are unable to sustain. In exploring its feeding grounds, where an enemy is likely to be encountered, the legs which carry the long claws are extended forward in front of the head or carried some what obliquely, their tips resting on the bottom, and the long, sensitive "feelers" are waved constantly back and forth to give warning of any foe or other objects which the eye may fail to detect. These are exclusively organs of touch. If the anticipated enemy makes his appearance, or if the animal is surprised, as when it is suddenly touched with the blade of an oar or cornered, it will immediately strike an attitude of defense. It now raises itself on the tips of its walking legs, lifts its powerful claws over the head after the manner of a boxer, and strikes with one of its claws at the offending object, trying to crush it or tear it to pieces. By far the most powerful organ of locomotion in the lobster is the tail, by the flexion of which it can scull itself through the water with astonishing rapidity. The lobster, though less active and keen-witted than the higher crabs, can not be regarded as a sluggish animal in any sense. In the water its movements are graceful; it is wary, resourceful, pugnacious, capable of defending itself against enemies which are often larger than itself, and, if the occasion requires it, of running about with the greatest agility and speed. When a lobster is surprised it seems to disappear with a single leap or bound, as a locust or grasshopper might do. It never, however, rises more than a few inches or at least a few feet above the bottom, and it is evident that swimming at the surface would be impossible, on account of the great weight of the body.

Jack Rabbits.—The jack rabbits, which occur almost everywhere in the Great Plains and desert regions of the United States, are so called—also "jackass hares" and "jacks," "narrow-gauge mules," and "small mules"—from the resemblance of their large ears to those of the jackass. They may be seen abroad. Dr. T. S. Palmer says in his account of them, at almost any hour of the day. Living as they do on the open plain, where they are compelled to rely for safety on quickness of hearing and on speed, their ears and hind legs are developed to an extraordinary degree. This gives them a somewhat grotesque appearance, but in reality few animals are more graceful than they as