Arenicola ecaudata 135 



"A. monfarfui" is a specimen o{ A. eeandata, it is in bad condition 

 and incomplete, but there is no doubt as to its species. 



In the memoirs cited of Profs. Marenzeller, Mesnil, Michaelsen 

 and Saint Joseph, ''A. hranchialis" included all the ecaudate forms 

 then described — e.g. ecaudata, hocckii, (jriihii, etc. 



Bionomics. — Arenicola ecaudata is not found burrowing in the 

 ordinary sand of the beach like A. marina; it occurs in the littoral 

 zone but chiefly in sandy, gravelly or muddy material among 

 stones, or in clefts at the base of rocks in the debiis formed by the 

 breaking down of the latter. A considerable amount of organic 

 matter is generally present in the material in which the worm lives. 

 The burrows of A. ecaudata and hrancliialis are oblique or sinuous 

 cavities, lined with a fair amount of mucus, and situated a few 

 inclies below the surface in gravel or lietween rocks and stones. 

 The castings of the worm, being composed of coarse material having 

 little coherence, soon fall apart. The well-known signs — the sand- 

 rope-like heap of castings and the funnel-like depression in the sand 

 — which indicate the presence of A. marina on countless sandy 

 beacbes, have no good counterparts in the case of the ecaudate 

 specie.s, in whicli both the castings and the mouth of the burrow are 

 inconspicuous among their surroundings. Whether these species are 

 present in any given area is therefore not obvious from a super- 

 ficial examination, as is often the case where A. marina is con- 

 cerned ; their presence can only be ascertained after careful, and 

 sometimes prolonged, search in likely places, such as those above 

 described. 



Little is known of the lial)its of A. ccav.dnta when it is covered 

 with water, but observations of Prof. Fauvel ^ are of interest in this 

 connection. He saw examples of A. ecaudata, which were kept in 

 an aquarium, leave the sand during the night to wander about at 

 the surface of the water, or to swim freely.^ Each was surrounded 

 by a tiiick envelope of mucus. On a light being brought near 

 the aquarium, the worms at once began to burrow into the sand, 

 leaving behind their mucous envelopes. 



Size. — Average specimens of ^. ecaudata, when normally extended 

 are about 130 to 180 mm. long. The longest seen by the ^vTiter was 

 255 mm. in length. When at first withdrawn from their burrows 



' M^m. Soc. Nation. Soi. Nat. Math. Cherbourg, xxxi (1899), p. 141. 

 - Cf. the remarks on the swimming of A. marina, p. 97. 



