6 W. T. CALMAN. 



symmetrical position of the dorsal languets to the left of 

 the middle line occurs according to Herdman in Distaplia 

 rosea, and Maurice describes the same arrangement in 

 Fragaroides. 



The branchial sac is connected with the wall of the atrium 

 by small trabeculse placed at the level of the interserial 

 lamellae (PI. 1, fig. 8). These are few in number, apparently 

 only one on each side for each lamella, though I could not 

 ascertain this with certainty. This condition presents the 

 opposite extreme to that seen in Fragaroides, where an 

 almost continuous membrane connects the branchial sac with 

 the body-wall between each row of stigmata. The wall of the 

 branchial sac, in contrast to that of Fragaroides, is here 

 entirely without muscles, except for the longitudinal bands 

 running in the lips of the endostyle and those at the sides of 

 the dorsal sinus. 



The minute structure of the interstigmatic bars agrees 

 perfectly with that described by Maurice for Fragaroides. 

 Along each side facing the cleft is the specialised stigmatic 

 epithelium (PI. 2, figs. 17 and 18), formed by six regular rows 

 of ciliated cells. Each cell forms at its free end a narrow 

 longitudinal ridge along which the cilia stand in a single row. 

 The surfaces of the bar turned towards the branchial and 

 atrial cavities are covered by simple flattened epithelium. In 

 the centre is a blood-sinus bounded by the basement membrane 

 of the epithelium. 



The endostyle is large and much undulated. In transverse 

 section (PI. 2, fig. 20) it shows essentially the same structure 

 as that of Fragaroides. The everted lips are covered by 

 ciliated epithelium. At the bottom of the groove a narrow 

 band of columnar cells bears the enormously long cilia charac- 

 teristic of the Ascidian endostyle. On each side of the groove 

 is the "glandular " epithelium, consisting of elongated curved 

 cells tapering towards their free ends, and this side wall of 

 "glandular" epithelium is divided into three parts by two 

 small bands of ciliated epithelium. These two bands are here 

 identical in structure, while in Maurice's account of Fraga- 



