28 



Animal Life by the Sea-shore. 



coating envelops the whole structure, concealing the spire, 

 which is visible in section (Fig. 25). 



Another assemblage of marine Gastropods consists of a 

 number of slug-like creatures, in which, as in the terrestrial 

 slugs, the shell is considerably reduced or absent (Fig. 27). 

 Perhaps the best-known British example of this section is 

 the Sea-hare (Aplysia punctata), often found at ver^' low 

 tide crawling over beds of sea-grass and sea-lettuce, and 

 browsing on these weeds (Fig. 26). It is a strange-looking 

 animal, often four or five inches long, of a deep purplish 

 black colour, with two pairs of tentacles on the head, the 

 larger pair, at the base of which the e^'es are situated, being 

 flattened and erect, suggesting the ears of a hare. The 

 shell is much reduced and not calcified, but flexible, and 

 partially covered by two lobes of the foot, which is reflected 



FIG. 26. SE.\-IIARE. 



over the mantle, the latter being folded beliind to form an 

 excretory siphon. When molested the Sea-hare has the power 

 of discharging a large quantity of purple fluid from the inner 

 surface of the mantle. The true Sea-slugs, belonging to the 

 chvision of Nudibranchs, or naked-giUed Gastropods, have no 

 shell at all in the adult condition, but the larger species possess 

 a very tough skin, strengthened with small, hard rods, known as 

 spicules. Such forms as Dons, Aeolis and Tri/onia are of great 

 beauty owing to their lovely pink, lilac, yellow or bright green 

 colours. Doris johnsloni is often found on rocky coasts, and 

 for its yellow blotches is popularly called the Sea-lemon ; its 

 body, reaching a length of three inches, is oval and flattened, 

 with two tentacles on the head and a rosette of retractile, 

 plume-like gills surrounding the vent or the hinder part of the 

 back. This rosette is not present in Aeolis and Tritonia. which 



