APPENDICULARIAE. 63 



and the blood appears to be entirely devoid of cellular elements. 

 The mouth opens into a spacious pharynx (Fig. 55), and leads 

 behind by a short oesophagus into a dilated stomach, from which 

 passes forward an intestine to open on the ventral surface by 

 the anus. The hind end of the intestine may be marked off as 

 a rectum. There is no pyloric gland or liver except in Stegosoma 

 and Megalocercus in which a gland, identified as liver, opens by a 

 narrow duct into the stomach. The pharynx has, on the anterior 

 part of its ventral wall, a short endostyle (o), consisting of a 

 groove bounded by large glandular cells without cilia except at 

 its front end. From the front end of the endostyle there arises 

 on each side a ciliated band which passes backwards and dorsal - 

 wards to join its fellow at the oesophageal opening. There is 

 no dorsal lamina and no row of tentacles. From the hind end 

 of the endostyle a ventral band of cilia, corresponding to the 

 ventral groove of other Tunicata, passes backwards to the oeso- 

 phageal opening. In the ventral wall of the pharynx behind 

 the endostyle are the internal openings of the two gill-apertures ; 

 these lead into two short ciliated tubes which open on the ventral 

 side of the body by the spiracles (n). There is a small ciliated 

 diverticulum of the dorsal wall of the pharynx, placed on the 

 right side of the ganglion and corresponding to the dorsal tubercle 

 of other Tunicata. 



The nervous system consists of a ganglion (Fig. 55) placed on 

 the dorsal side of the anterior wall of the pharynx, and of a 

 dorsal nerve cord (d) which passes back from the ganglion on 

 the right side of the stomach to the tail. In the tail, to the 

 hind end of which it extends, the dorsal cord lies on the left side 

 of the notochord and presents a variable number of swelhngs 

 due to the presence of nerve cells and called caudal ganglia. 

 The number of these caudal ganglia varies from eight to forty. 

 The first of them is usually larger than the others. Nerves are 

 given off by the cerebral ganglion, and by the caudal ganglia. 

 It has been stated that the cerebral ganglion and dorsal cord 

 contain a minute canal, but this is doubtful 



The position of the caudal nerve cord on the left side of the notochord 

 has suggested the view that the tail has undergone rotation through 90 

 so that its true dorsal surface has come to lie to the left. 



An otolithic vesicle (a) lies on the left side of the ganglion, so 

 closely in contact with it that at one place the inner wall of the 



