Page:Natural History, Mollusca.djvu/120

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108
NUDIBRANCHIATA.—DORIDIDÆ.

forming a ribbon. The ribbon adhered by its edge to the rock in an oval spire. One which I found measured nearly twenty inches in length, and half in breadth. By counting how many balls were contained in a tenth of an inch in the row, and how many rows in an equal length of the ribbon, on the most moderate computation there were six hundred thousand eggs. Yet this Doris was certainly not very common; although I was often searching under the stones, I saw only seven individuals."[1]

When we meet with accounts like this of the exceeding multitude of eggs produced by some species of animals, we are apt to wonder that the world is not filled with them, and to ask what becomes of these immense hosts. The fact is, they form the food of other creatures, a vast multitude—perhaps nine out of every ten—being devoured as soon as they are born. What Mr. Peach says of these very embryos, I have myself often observed in those that I have endeavoured to rear. They " have myriads of enemies in the small Infusoria, which may be noticed with a powerful microscope hovering round them, and ready to devour them the instant weakness or injury prevents their keeping in motion the cilia, which serve both for locomotion and defence. Let them cease to move, a regular attack is made, and the animal is soon devoured; and it is interesting to observe several of the scavengers sporting in the empty shell, as if in derision at the havoc they have made."[2]

The largest British species of this genus is D. tuberculata, often called the Sea Lemon. It

  1. Voyage of Adventure and Beagle, iii. 258.
  2. Annals of N.H, xv. 446.