REPORT ON THE TUNICATA. 157 



I regard this organ as corresponding to the conjoined su1)ueural (or hj^ophysial) 

 gland and dorsal tubercle of other Ascidians. In place of there l3eing a branched 

 tubular gland communicating by a single duct with the single ciliated opening of the 

 dorsal tubercle, as in most Ascidians, or by a number of ducts with numerous secondary 

 openings into the peribranchial cavity, as in Ascidia mammillata, there are in the 

 present case a number of simple tubular glands each of which opens to the exterior Ijy 

 its own ciliated iufundibulum. 



Although this arrangement seems at first very dilferent from that of a typical 

 Ascidia, still there are intermediate forms known through which a passage can be 

 traced. I described in 1882 * in the case of Cynthia irregularis a dorsal tul)ercle 

 where more than one opening was present, and since then Sluiter ' has described a 

 similar condition in Ascidia canaliculata and in Styela cryptocarpa, while in Boltenia 

 pachydermatina, as several investigators have pointed out, the surface of the large 

 dorsal tubercle is broken up by ridges into a number of openings. Then again in 

 Ascidia mammillata, as described by Julin^ and by myself,* in Ascidia marioni 

 according to Eoule,^ and in Polycarpa sulcata as shown by von Drasche,* the subneural 

 gland has a number of ducts wdiich open separately to the exterior,' thus leading to the 

 present case, where each tubule of the gland has a separate ciliated opening on the 

 surface of the dorsal tubercle. 



Both on account of the comparative simplicity of this last arrangement, and 

 also on account of its proximity to and direct connection with the free surface, 

 the condition described above in this large Ascidia from Kerguelen is probably 

 the nearest to the primitive condition of the organ ; and it appears to indicate 

 that the subneural gland and dorsal tubercle are derived from a group of simple 

 tubular glands opening close together on the dorsal edge of the anterior end of the 

 pharjTix. Such an origin would tell equally against the recently expressed view * that 

 the dorsal tubercle was originally an organ for aerating the central nervous system, and 

 against the former theories that it was the duct of a cephalic renal organ, or a 

 buccal sense-organ, or a combination of the two ; ' but would seem to support the 

 opinion of Roule,'" that the subneural gland and dorsal tubercle are to be regarded 

 merely as a more or less complicated mucous gland and its duct. 



1 This Report, Part I. p. 141, pi. xvi. fig. 12. 



' Natuurkund. Tijdichr. v. Nedtrl. Indie, Dl. xlv. pp. 17i and 2h), 1S85. 

 ■■' Archives de Biologie, torn. ii. p. 21-1, 1881. 

 * Joum. Linn. Soc. Land. (Zool.), vol. xvi. p. 580, 1882. 

 ■■■ Aim. Mus. Hist. Nat. Marseille (Zool.), torn. ii. p. 240, 1884. 

 " Deiil-schr. d. k: Ak-ad. d. Wiss. Wicii, Bd. xlviii. p. 379, 1884. 



' The place of opening may be the peribranchial cavity (^Ascidia mammillata), the branchial sac (^Ascidia marioni), 

 or the peritubercular area {I'vlycarpa sulcata). 



' Lilian Sheldon, Quart. Journ. Micr. Sci., vol. xxviiL p. 131, 1887. 

 s Herdman, Proc. Biol. Soc. Liccrpuol, vol. i. p. 22, 1887. 

 '» Roule, op. cit., p. 102, 1884. 



