XVII 



HABITS OF LINGULA 



483 



animal has with the world around it is 

 by means of the currents set up by the 

 cilia on the tentacles. 



In spite of the absence of any definite 

 eyes, Thecidium^ according to Lacaze- 

 Duthiers, is sensitive to light ; he noticed 

 for instance that, when his shadow fell 

 across a number of these animals he was 

 watching in a vessel, their shells, which 

 had been previously gaping, shut up at 

 once. 



In Cistella the tentacles can be pro- 

 truded from the open shell, and in Rliyn- 

 clioneUa the spirally-coiled arms can be 

 unrolled and extruded from the shell, but 

 this does not seem to have been observed 

 in other genera, with the possible ex- 

 ception of Lingida. The food of these 

 animals consists of minute fragments 

 of animal and vegetable matter, a very 

 large proportion of it being diatoms and 

 other small algae. 



Lingula differs markedly from the 

 other members of the group, inasmuch 

 as it is not firmly fixed to a rock or 

 some such body by a stalk or by one of 

 its valves, but lives in a tube in the 

 sand. Some recent observations of 

 Mons. P. Francois ^ on living specimens 

 of Lingula anatifey^a which he found 

 living in great numbers on the sea- 

 shore at Noumea in New Caledonia 

 may be mentioned. The presence of 

 the animal is shown by a number of 

 elongated trilobed orifices which lead 

 into the tube in which the Lingula lives. 

 The animals, like most other Brachi- 

 opods, live well in captivity, and he was 

 able to watch their habits in the aquaria 



a^ 



Fig. 321. — Figures illustrating 

 the tubes in which Lingula 

 anatifera lives. The upper 

 figure is a view of the tri- 

 lobed opening of the tube. 

 The lower figure shows the 

 tube in the sand laid open 

 and the animal exposed. 

 The dotted line indicates the 

 position of the body when 

 retracted. The darker por- 

 tion is the tube of sand ag- 

 glutinated by the secretion of 

 the stalk. (After Franyois.) 



1 "Choses de Noumea," Arch. d. Zool. exp. et gen., 2ud ser., vol. ix., 1S91. 



