108 NUDIBRANCHIATA.—DORIDIDA, 
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.” * 
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 be- 
comes 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. The 
‘“‘have myriads of enemies in the small Jnfusoria, 
which may be noticed with a powerful microscope 
hovering round them, and ready to devour them 
the instant weakness or injury prevents their keep- 
ing in motion the cilia, which serve both for loco- 
motion and defence. Let them cease to move, a 
regular attack 1s made, and the animal is soon de- 
voured ; 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.’’ ft 
The largest British species of this genus is 
D. tuberculata, often called the Sea Lemon. It 
* V oyage of Adventure and Beagle, iii. 258. 
{¢ Annals of N.H. xv. 446. 
