624 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVU. 



NOTE ON THE PROBABLE USE OF THE ANTENNUL.E ]N ALBUNEA 



AND LEPIDOPA. 



The great length of the antennuhe in Albunea and Lepidopa led to 

 a rather interesting experiment to ascertain as far as possible the 



special use of organs so extraordinarily 

 developed and so different from those in 

 other Decapod Crustacea. 



In the tirst place it must be borne in 

 mind that the antennulaj in Albunea are 

 from two to three times the length of 

 the carapace, while in Lepidopa the}' are 

 often live times as long. An examina- 

 tion shows that the lateral motion is 

 slight while the motion in the other di- 

 rection is very free and strong, the fla- 

 gellum easily changing from a direction 

 vertical to the carapace to an opposite 

 direction, or through an arc of more than 

 180 degrees. This motion is provided 

 for by the peduncles, which are com- 

 pressed, presenting an edge to the sand 

 in one direction and a relativeh^ broad 

 and flattened surface in the other. The 

 flagelli are very stiff', the outer one-third 

 only acting as a true leash. 



The experiment, if so it can be called, 

 consisted in placing an alcoholic speci- 

 men of Albunea in a nearly vertical 

 position in clean white sand, until only 

 the cornea and the antennulte were ex- 

 posed. In this natural position the 

 antennuhe seemed to lie upon the surface 

 of the sand nearly perpendicular to the 

 lower surface of the specimen. Alcohol 

 was then added in sufficient quantity to 

 cover the specimen, when it was noticed 

 that the sand was held back from the 

 mouth parts by the numerous stiff' hairs, 

 the hair along the flagelli preventing its 

 washing in between them. These seemed 

 to be placed there for that purpose, for, 

 arranged in two rows at nearl}^ right 

 angles to each other, the angle so formed opposes the open angle of the 

 other flagellum. The hairs are longer near the base, l)ecoming short 

 near the more flexible outer ends. The result of this arrangement is 



Fig. 3.— Albunea gibbesii, partially 

 covered avith sand. (much en- 

 LARGED.) 



