LEPAS 379 



on the ventral side. Within the mantle cavity lies the body, turned 

 over on its back with the appendages upwards (or downwards, as the 

 animal hangs) and connected with the peduncle and mantle only at the 

 extreme anterior end, where there is a preoral adductor muscle by which 

 the sides {valves) of the mantle can be drawn together and so the 

 opening closed. The antennae, which should be somewhere in this 

 region, are absent. The prominent mouth is overhung by a large 

 labrum. At its sides stand the mandibles, which have a flat, toothed 

 process towards the mouth and a large, uniramous, foliaceous palp^ 

 and the maxillules, simple structures with a fringe of strong bristles 

 on the notched median edge. A pair of simple, hairy lobes, united by 

 a median fold, which shut in the mouth and its appendages from be- 

 hind, represent the maxillae. The six pairs of thoracic limbs or cirri 

 have each two long, many-jointed, hairy rami, curled towards the 

 mouth. They are successively longer from before backwards. A 

 couple of filamentous epipodites ("gills") stand on the protopodite 

 of the first pair. Behind the cirri stands a long median ventral penis ^ 

 and behind this again is the anus, with a pair of vestigial caudal rami. 



The animal feeds by thrusting out the cirri through the mantle 

 opening and withdrawing them with a grasping motion, whereby 

 particles are gathered from the water by the setae upon the limbs. If 

 it be molested the motion ceases and the valves are drawn to. The 

 alimentary canal has an oesophagus (stomodaeum) directed forwards 

 from the mouth to the long wide stomach which bears several coeca 

 around its commencement and tapers behind into an intestine. Com- 

 plicated maxillary glands open on the maxillae. There is no heart or 

 system of blood vessels. The nervous system has a suboesophageal 

 ganglion, and a separate ganglion for each pair of cirri behind the first. 



Lepas is hermaphrodite. The ovaries lie in the peduncle and the 

 oviducts open on the bases of the first pair of thoracic limbs, much 

 further forwards than is usual in Crustacea. The testes are branched 

 tubes which lie at the sides of the alimentary canal and in the basal 

 parts of the cirri. Each vas deferens enlarges into a vesicula seminalis 

 whose duct joins that of its fellow in the penis. Impregnation takes 

 place by the penis depositing a mass of spermatozoa on either side 

 of the mantle cavity of a neighbouring individual, near the opening 

 of the oviduct. It is possible that isolated individuals may be self- 

 fertilized. The ova undergo their early development within the mantle 

 cavity of the mother attached in a flat mass, the ovarian lamella, by 

 a glutinous secretion manufactured by the terminal enlargement of 

 the oviduct, to a fold of the mantle which projects on each side from 

 near the junction with the body and is known as an ovigerous frenum. 



The young are set free as Nauplii, characterized, as are those of 

 nearly all cirripedes, by a pair of lateral frontal horns , on each of which 



