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Show 98 HABITS OF WORMS. CrrAP. II. To sum up, as chance does not determine the manner in which objects are drawn into the burrows, and as the existence of specialized instincts for each particular case cannot be admitted, the first and most natural supposition is that worms try all methods until they at last succeed ; but many appearances are opposed to such a supposition. One alternative alone is left, namely, that worms, although standing low in the scale of organization, possess some degree of intelligence. This will strike every one as very improbable; but it may be doubted whether we know enough about the nervous system of t.he lower animals to justify our natural distrust of such a conclusion. With respect to the small size of the cerebral ganglia, we should remember what a mass of inherited knowledge, with some power of adapting means to an end, is· crowded into the minute brain of a worker-ant. Means by which worms excavate their burrows.-This is effected in two ways; by pushing away the earth on all sides, and by swallowing it. In the former case, the worm inserts the stretched out and attenuated CnAP. II. EXCA V A'l'ION OF TIIEIR BURROWS. 99 ante~ior extremity of its body into any little crevJCe, or hole; and then, as Perrier remarks,* the pharynx is pushed forwards into this part, which consequently swells and pushes away the earth on all sides. The anterior extremity thus serves as a wedge. It also serves, as we have before seen for prehension and suction, and as a tactile o;gan. A worm was placed on loose mould, and it buried itself in between two and three minutes. On another occasion four worms disappeared in 15 minutes between the sides of the pot and the earth, which had been moderately pressed down. On a third occasion three large worms and a small one were placed on loose mould well mixed with fine ~and and firmly pressed down, and they all disappeared, except the tail of one in 35 minutes. On a fourth occasion six l~rge worms were placed on . argillaceous mud mixed with sand firmly pressed down, and t~ey ~i appeared, except the extreme tips of the tmls of two of them, in 40 minutes. In none of these cases, did the worms swallow as far as could. be seen, any earth. The; * 'Archives de Zoolog. exp6r.' tom. iii. 1874, p. 405. H 2 |