Sea-slugs 299 



The remaining families are .small, and both genera 

 and species few. 



The Crimson Herma3a (Hermrea bifida) is very 

 slender in proportion to its inch of length, with a row 

 of leaf-like cerata down each side. The body is trans- 

 parent, tinged with pale yellow, or greenish. The 

 single pair of short tentacles are folded lengthwise, 

 so that they present the appearance of a tube that 

 is split down one side. The cerata are transparent 

 pink, permeated by much - divided branches of the 

 liver, which take on the colour of the food recently 

 eaten. This species and the next appear to be 

 vegetable feeders, and the favourite haunt of the 

 Crimson Herma3a is anion o; the small crimson weeds 

 just below low water. It may commonly be found 

 upon Delesseria, where it is very inconspicuous, for 

 its cerata are just like small shooting fronds of that 

 weed. It has large eyes, and it is apparently very 

 sensitive to changes of light, for a shadow passing 

 over the creature will at once cause it to contract 

 itself, draw in its head and erect its cerata, evidently 

 for the purpose of putting on a fierce aspect. At the 

 same time it ejects a nauseous fluid. The other 

 species is the Green Hermaea (H. dendritica), a much 

 smaller species — about one-third of an inch in length 

 — of pale green colour marked w4th branching lines 

 of deeper green similar to the veining of a leaf. The 

 slender cerata are in eight rows along each side ; 

 transparent, with a sprinkling of opaque white, and 

 with the central vessel green, the contents lobed, so 

 that the cerata appear to be banded crosswise. It 

 feeds upon green weeds such as the delicate Bryoj)sis 

 'plumosa, Codiiim, Enteromorpha, and Ulva, The 



