PEOF. W. A. HERDMA.X OK BEITISH TXTNICATA. 445 



communicated a note at the last meeting of the British Associa- 

 tion (Edinburgh) somewhat as follows : — 



In the interesting paper ('Bulletin Scientifique,' July 1892) 

 by Dr. C. Julin, which forms the first part of his ' Les Ascidiens 

 des Cotes du Boulonnais,' I notice it is stated, on page 30, 

 " L'existence d'une couronne de tentacules circumcloacaux n'a 

 jamais, a ma connaissance du moins, ete signalee chez aucune 

 espece d'ascidien simple ou compose." If it has escaped Julin's 

 attention that I described and figured atrial tentacles in 1882 

 in a simple ascidian, and in 1886 in a compound one, then I fear 

 it may have escaped notice altogether, perhaps because, along 

 with some other anatomical observations and some theorstical 

 conclusions and suggestions, it is buried iu the ' Challengei' ' 

 reports in a mass of detailed descriptions of new species. At 

 any rate, the existence of atrial tentacles is evidently so little 

 known that the following brief notes upon what I have seen of 

 them may be of interest. 



In the simple ascidian Bathyoncus mirahilis from the Southern 

 Ocean, at a depth of 1600 fathoms, there are two circlets of 

 minute tentacular processes which project from the inner surface 

 of the cloacal wall close to the atrial aperture. These atrial 

 tentacles are all of the same size, and are placed at about their 

 own length apart (see ' Eep. Tun. Chall, Exp.' part 1, vol. vi., 

 1882, page 167, and pi. xxiv. fig. 12, at.t.). 



The ascidiozooids of the compound (?) ascidian, Goodsiria 

 placenta, from the Cape of Good Hope, have also atrial tentacle?, 

 very much like those of Bathyoncus mirahilis, but forming a 

 siagle series. In the original description {op. cit. part 2, vol. 

 xiv. 1886, page 331, and pi. xliii. fig. 10) I wrote as follows : 

 " At the base of the atrial siphon, where the invaginated layer 

 of test ends, there is a slight ridge which bears a series of small 

 tentacles projecting freely into the peribranchial cavity. These 

 atrial tentacles are much smaller than the ordinary or branchial 

 tentacles, and there are only twelve of them. The position of 

 the atrial tentacles in relation to the atrial siphon corresponds 

 exactly to the position of the branchial tentacles at the base of 

 the branchial siphon, but their use at the entrance to the peri- 

 branchial cavity is not obvious. It has been observed in some 

 simple ascidians that the current of water which usually flows 

 in at the branchial aperture and out at the atrial is occasionally 

 reversed for a short period, the atrial aperture becoming inhalent. 

 Possibly in the present species this habit may have become so 



