a study of their development shows that they originate from the same kind of substance.
Several species of skates from our own seas have an electric organ in the tail, a fusiform body, about half way up the tail of the fish, in contact with the skin, and partly enveloped in a well-known muscle—the sacrolumbalis muscle. This organ shows a disc-like structure, somewhat similar to that found in the electrical organs of the torpedo and gymnotus, but more resembling the latter than the former. There can be no doubt again that we may view the electrical organ of the skate as a modified muscular apparatus.
I shall now ask Mr. Brodie to show you sections of these organs by the electric microscope. [This was done, and a demonstration was given, which is partially illustrated by the Figs. 73, 76, 77, 80, and 81.]
But nature shows often a remarkable power of modifying different parts for the same purpose, or of similar parts for different purposes. This is seen both in plant and animal life. Thus the tendrils by which a plant clings to other structures may be modified leaves, stipules, or branches; and, on the
