Mr. A. Adams on the Animal and Float of lanthina. 419 



floats shell downwards, with the vesicular buoy above it directed 

 backwards. The anterior part of the foot is mobile, free, rounded, 

 and dilated, and the sides are usually folded inwards, forming a 

 shallow cup, which embraces the smooth anterior rounded end 

 of the float. When the animal wishes to bring its head to the 

 surface of the water, this part of the foot is made to glide over 

 the back of the float. Thus the animal can raise and lower itself 

 at pleasure by means of its own float. 



The violet liquid which is ejected in considerable quantities 

 when the animal is irritated is at first equably difi*used, but 

 shortly sinks to the bottom in the form of a deposit, leaving the 

 water pellucid. The bag or reservoir containing the colouring- 

 fluid is visible through the skin on the back of the neck, and 

 the fluid is poured direct into the branchial cavity, and makes 

 its escape from under the free edge of the mantle. My dyeing 

 operations with this purple fluid were not crowned with success, 

 the beautiful colour fading gradually away, leaving " magenta " 

 and " mauve " yet possessors of the field. 



The float is attached to the under surface of the caudal end of 

 the foot, where what appear to be the muciparous follicles give 

 it a striated appearance. In this species, which is /. violacea, 

 the float is quite colourless ; but in /. exigua it is of a faint 

 pinkish tinge, and in that of /. glohosa it is frequently of a pale 

 delicate lilac. In Reclusia Bensoni, A. Ad., which has a pale 

 yellow shell, the float is of a light straw-colour. 



None of the floats of my specimens had ova affixed to them; 

 but the surface of many of the shells was studded with the 

 young of LepadeSf which appeared to me to have been described 

 as a genus of Entomostracans, under the name of Evadne, 

 When the animal is weakly or dead, the float readily becomes 

 detached, for there is no organic connexion between it and the 

 foot. The mucous film of which it is composed appears to be 

 of the same nature as that glutinous fluid emitted by Litiopa 

 and Alaba, but which, in these genera, instead of forming vesi- 

 cles containing air, is spun out into filmy threads, which, how- 

 ever, are sufficiently buoyant to support the animals. The vesi- 

 cles are probably formed in the same manner as the frothy spume 

 of the little green Homopterous larva which is seen on bushes 

 in the spring, and which, in Hampshire, usually goes by the 

 name of *^ Cuckoo-spit.'^ When a portion is cut ofi\, the float 

 is enlarged at the end next the foot of the animal, and is not 

 regenerated at the excised part. 



The float is often seen lacerated by the teeth of fishes ; and 

 hundreds of detached floats are observed in the water. With a 

 pair of sharp-pointed scissors I made incisions into the floats, 

 and allowed the air to escape, when th6 animals gradually 



28* 



