96 MICROSCOPICAL STUDIES. 



row of stiff hairs. Each is biramose, i.e. composed of two branches, 

 which arise from a single stout basal joint, the protopcdite. 



Alimentary Canal. The mouth opens into a short straight 

 oesophagus, leading into a capacious stomach, beset at the anterior 

 end with glandular diverticula (liver). Posteriorly the stomach 

 narrows gradually to merge into a long intestine, with anus opening 

 on the dorsal face of the truncated abdomen. Food is obtained by 

 the sweeping motion of the thoracic appendages, which by alternate 

 protrusion and retraction sweep inwards towards the mouth such 

 microscopical food as suffices. 



The nervous system is limited to a paired cerebral ganglion 

 and a short ventral chain of 5 paired ganglia. Except a double pig- 

 ment-spot representing the eyes, no definite sense organs are known. 

 In the isthmus attaching the main body mass to the mantle, is 

 a strong transverse adductor muscle connecting the scuta of opposite 

 sides. By means of this, are controlled the opening and the closing of 

 the mantle cleft through which are protruded the cirriform feet. 

 Numerous other muscles are also found in the posterior head region, 

 chiefly concerned in controlling those movements of the body which 

 alternately elevate and depress the limbs and allow their sweeping 

 motion to perform at fullest advantage. In the walls of the peduncle 

 we also find strong muscles, having a longitudinal arrangement. 



Reproduction. Lepas is hermaphrodite, possessing both testcs 

 and ovaries. The former consist of ramified arborescent whitish 

 tubules lying along either side of the digestive canal and penetrating 

 even into the basal joints of the limbs. The product of these glands 

 is gathered into canals tributary to larger, which finally pour it into 

 two conspicuous milk-white seminal vesicles, whose vasa differentia 

 run separate almost to the base of the penis. At this point the two 

 unite and form a common ejaculatory duct passing through the penis. 

 The ramified ovaries, purplish in colour, lie within the posterior 

 portion of the peduncle, and the two oviducts (ov. Fig. 7) after 

 passing through the isthmus, open, one on either side of the head, at 

 the base of the first pair of thoracic feet a forward position wholly 

 exceptional among Crustaceans where the usual position for the 

 female orifices is upon the first abdominal segment among the lower 

 forms (Copepods, &c.), while in the higher (Malacostraca), it is 

 constant to the antepenultimate thoracic segment. 



The ova when extruded become cemented together into two 

 large purplish plate-shaped masses enfolding the main body region. 

 These plates are nearly always present, and on removing the mantle 

 are most conspicuous objects. Two small simple folds of the mantle 

 integument the ovigerous frena arising close to the isthmus, 

 furnish attachment to these ova masses, and prevent them being 



