268 POPULAR HISTORY OF THE AQUARIUM. 



or breathing-apparatus consists of variously shaped organs, 

 arranged on different parts of their sides and bodies, but 

 all external. Some of them from their complicated branch- 

 ing gills are almost like moving trees, or more like Slugs 

 with a forest on their backs ; others are of plainer make, 

 and have the gills exscrted, in the form of a branched star, 

 through the mantle. A few of the forms are represented 

 in the Plate. The following are Mr. Gosse\^ observations 

 on one of the species, as to its habits and reproduction. 



'' Doris bila]\iellata, 



" Of which there were three in the vessel, was very social 

 in confinement, continually finding out one another and 

 crowding close up together. They crawl round the pan, 

 generally resting close to the surface, often with the mantle 

 a little raised, so that the air may reach the body. 



'"'Feb. £2ud. The Doris hilamellata laid a ribbon of spawn, 

 attached to the side of the pan, almost at the surface of the 

 water; it adhered by one edge, and formed an imperfect 

 spine or cup, the ribbon being bent upon itself, the upper 

 edge or brim leaning a little outward and being puckered. 

 The general substance is white and opaque, owing to a vast 

 number of minute eggs enveloped in a clear jelly. The 



