508 THE AQUARIAN NATURALIST. 



cient locomotive apparatus; these are fringed with 

 long cilia, by the motion of which the minute being 

 swims freely through the water : they are capable of 

 being withdrawn into the shell and the operculum 

 closed upon them. The mouth is situated between 

 these lobes. 



From the above description it will be at once seen 

 that these little ' ' Nautilines " do not bear even the 

 most remote resemblance to the future Doris-, and 

 how long they remain in this state, or how their 

 transformation takes place, is a very interesting sub- 

 ject of inquiry. In the second stage of growth, the 

 diminutive Nudibranch is still found enclosed in its 

 shell ; but the mantle has become detached, and covers 

 tightly the mass of the viscera. The foot is so en- 

 larged, that it forms a considerable projection beyond 

 the margin of its operculum eyes and tentacles be- 

 come conspicuous, and the tiny voyager swims with 

 surprising quickness. 



In the third stage the shell has fallen off", and the 

 general shape is that of the parent, but the ciliated 

 locomotive lobes still remain. In the fourth stage 

 the creature begins to crawl in the Gasteropod 

 fashion, until at length the full evolution of its 

 organs completes the metamorphosis, and entitles the 

 animal to the privileges of maturity. 



Few, however, of such a multitudinous host are per- 

 mitted to arrive at this stage of their existence. The 

 young ' ' Nautilines " have myriads of enemies in the 

 shape of small infusoria, which may be noticed with a 

 powerful microscope hovering round them, and ready 

 to devour them the instant weakness or injury pre- 



