290 STUDIES ON TUNICATA, 



irregularity of the transverse and interstigmatic vessels makes it 

 difficult to describe the mantle in detail. Each fold bears four 

 or five internal longitudinal vessels, and there are either three or 

 four in the interspaces; these latter are finer than those on the 

 folds, and are close together beneath the folds; in the preparation 

 photographed (PI. xxvi., fig. 8) they have been brought into view 

 by cutting away a fold. The arrangement of transverse and 

 interstigmatic vessels is almost regular and rectangular on the 

 folds, but is very irregular in the interspaces; true vortices are 

 rare; only one is shown in the microphotogra,ph at the top. 



2'he endostyle extends from the dorsal end of the sac to the: 

 circumoesophageal bands without undulation. The circumceso- 

 phageal bands have a very undulatory course (Pl.xxv., fig.4). 



The dorsal lamina (Pl.xxv., fig.4) is a simple membrane, not 

 ribbed or toothed. Owing to the approximation of oesophageal 

 and branchial apertures, the lamina is short; apparently it does 

 not extend beyond the former aperture dorsally. 



The dorsal tubercle (PI. xxv., fig.4) is somewhat rhomboid in 

 outline, with \yell rounded corners. The aperture upon it is 

 sigmoid, each arm ending against an oval opaque-white area. 

 The lips of the aperture are opaque-white, due to the closely 

 packed cilliated cells lining it; and the two areas at the ends of 

 the arms are apparently ovoid chambers, probably similarly 

 lined. 



The tentacles are about sixteen or twenty in number, they are 

 arched over and completely close the branchial aperture. Each 

 tentacle consists of a stout tapering racbis about 3 milli- 

 metres long, and 0-3 of a millimetre broad at its base, 

 bearing on either side a series of pinnae, which in turn bear 

 pinnules; the pinneeof the base are scarcely longer than those of 

 the apex; their pinnules may bear secondary pinnules. The 

 length of the central rachis varies slightly, but without regularity. 



The genital glands are situated on either side of the body; that 

 on the left side is in two portions, one of which is situated in the 

 rectal loop, the other posterior to the intestine (PI. xxvii., fig. 11). 

 The second gland is situated in the middle of the right side; all 

 are attached to the mantle. 



