114 BRITISH TUNICATA. 



narrow, and is ribbed on the right side : the tubercle 

 is minute , and in the form of a loop open in front ; the 

 extremities are pointed. The tentacular filaments are 

 very slender, long, and numerous ; they do not vary 

 much in length and are closely set in a single line, 

 but have in front a few quite short filaments. The 

 oral lamina has the fringe of tubercular points on the 

 left of the mouth well developed, the free points being 

 rather large. 



The ovary is situated on both sides of the intestine, 

 but chiefly on the left side towards the upper extremity 

 of the loop ; it is a rather delicately-branched organ, 

 so arranged as to have the appearance of an open 

 reticulation. The male casca are very minute, and are 

 placed on the left side of the intestine and stomach ; 

 but it must be observed that in the specimen examined 

 the reproductive organs were not fully developed. 

 The cells coating the stomach are large. 



This species is evidently related to A. aculeata, but it 

 is distinguished by many characters. Besides the very 

 elongated form, the attachment is different and the 

 test only slightly tuberculated. The tentacular fila- 

 ments are differently arranged, and the minute struc- 

 ture of the branchial sac is quite peculiar and alone 

 sufficient for specific distinction. 



16. Ascidia aculeata Alder. 



(PL VII, figs. 9-11 ; PI. XVIII, fig. 1 ; PL XIX, 



fig. 9.) 



Ascidia acuhata ALDER in Ann. Nat. Hist. (3) XI [1863], 

 p. 156. 



Body ovate, depressed, greenish, attached more or 

 less by the side to sea-weeds or zoophytes. Apertures 

 nearly sessile, aculeated, the branchial terminal, the 

 anal one-third down the side. Test thin, transparent, 

 greenish or nearly colourless, covered with aculeated 

 tubercles most prominent on the upper or left side, 

 greenish, transparent, showing the reticula- 



