2 92 Shell Life 



the resemblance, for both are well protected. All the 

 Sagartias are provided with stinging-threads, which 

 are shot out from their tentacles with great force 

 and rapidity and are able to pierce the shells of 

 shrimps and the scales of small fishes ; in addition 

 they are mostly unpleasant to the taste and smell. 

 This would be a good reason why ^^]olis which feeds 

 upon anemones should mimic Siujartid', but the case 

 is complicated by the fact that ^olis, as we have 

 seen, has also stinging cells at the tips of its cerata, 

 and is known to be otherwise unpalatable to fishes. 

 The Plumed ^olis is among the most active of the 

 Sea-slugs, gliding and swimming with equal ease. 

 It is subject to considerable colour variation, and this 

 is affected to a large extent by the colour of their 

 food. We have found that the paler, rose-tinted 

 variety found on the Cornish coast clianged in 

 confinement according to the colour of tlie anemone 

 we allowed it to eat. 



Alder's Little ^olis {jE. alderi) was first dis- 

 covered by Mr. W. P. Cocks at Falmouth. It is only 

 about I inch lonof, and has about fifteen rows of 

 cerata on each side. These vary from greenish fawn 

 colour to dark brown with pale ^^ellow tips. Owing 

 to the small amount of liver in the first two rows of 

 cerata, these form a white frill behind the head, which 

 is a very distinct character witli this species. On 

 being touched the head is immediately withdrawn 

 into the body, and the cerata are erected, until the 

 creature bears a striking likeness to a small anemone 

 often found in its neighbourhood. jE. glaiica is much 

 larger than the last (nearly 2 inches), and its broad 

 foot suddenly finishes behind in a sharp point. The 



