REPORT ON THE TUNICATA. 49 



I am doubtful how far the number and position of the stigmata can be taken as a 

 diagnostic character in these species of Doliolum. Possibly there may be a certain 

 amount of individual variation. It is evident that Doholum denticulatum, Q. and G., 

 DoIioJnm chrenhergi, Krohn, Doliolum gegenhauri, Uljanin, Doliolum tritonis, Herd- 

 man, and the two new species Doliohim affine and Doliolum challengeri, are all closely 

 allied; and, on the other hand, Doliolum miilleri, Krohn, Doliolum rarum, Grobben, 

 and the new species Doliolum krohni, described below, are also closely related to one 

 another ; but whether these nine species are all distinct, or whether they might not be 

 better arranged as so many varieties of two species, Doliolum denticulatum and 

 Doliolum, miilleri, is a question which will have to be discussed when we know more 

 about their characters in the various stag-es of their life-histories, and when we know 

 the rano-e of their individual variations. 



Doliohiiu Icruhui, n. sp. (PI. III. fig. 1). 



Body of the usual cask-like form. 



Mantle having the usual eioht muscle bands. 



Branchicd Sac with comparatively few stigmata, which are restricted to the 

 posterior end of the sac. There are about twenty -five pairs, which run in an o1)liquc 

 liand posteriorly and dorsally from a little in front of the fifth muscle Ijand to a little 

 behind the sixth. 



Endostyle extending from tlie second muscle hand nearly to the fifth. 



I refer to this new species the following specimens : — 



(1.) December 14 and 15, 1875 ; South Pacific, oflF Valparaiso ; lat. 33° 31' 0"— 33° 

 12' 0" S., long. 74° 43' 0"— 76° 29' 0" W. ; surf. temp. G2°— G2°-5 ; about 

 thirty specimens. 



(2.) Two microscopic slides mounted during the expedition. From same locality 

 as (1). 



This species is related to Doliolum miilleri, Krohn, and Doliolum rarum, Grobben, 

 as all three species are characterised by having the stigmata in the l^ranchial sac 

 restricted to the posterior end of the organ. In Doliolum varum there are only five 

 pairs of stigmata. In Doliolum miilleri there are ten to twelve pairs, and they form a 

 band wliicli runs dorso-ventrally midway between the fifth and sixth muscle bands, and 

 nearly parallel to them. In the present species (see PI. III. fig. 1) there are twenty-five 

 pairs of stigmata, forming an inclined baud crossing both fifth and sixth muscle bands 

 as it runs posteriorly and dorsally. The posterior extremity of the endostyle reaches 

 ])ack almost to where the stigmata commence. 



(zooL. cnAi.L. Exr. — PAHT i.xxvi. — 1888.) Gggg 7 



