1895. RESULTS OF '' CHALLENGER" EXPEDITION. 67 



The Tunicata. 



The large collection of Tunicata made during the Expedition has 

 added greatly to our knowledge of this group, as regards both its 

 morphology and its distribution. The pelagic tunicates (Salpidae, 

 Doliolidae, and Pyrosomidae), which form an important constituent of 

 the surface fauna of the ocean, have, on account of their abundance 

 and the comparative ease with which they may be obtained, attracted 

 the attention of naturalists and voyagers in many parts of the world. 

 Hence the " Challenger " collection of these forms contains com- 

 paratively few novelties ; but it is of considerable value, since, from 

 the constancy and care with which tow-net observations were 

 conducted, and their results preserved, it affords much additional 

 information as to the distribution of these pelagic Tunicates horizon- 

 tally, and to a less degree vertically. One noteworthy form is the 

 new species Pyvosoma spinosuni, of which a magnificent specimen, over 

 four feet in length, was obtained in the North Atlantic, but was un- 

 fortunately not preserved entire. The remarkable new genus, 

 Octacnermis, described first by Moseley, of which two species are 

 known, seems to be an abyssal and considerably modified ally of the 

 pelagic Salpidae. A new family, the Octacnemidae, has been formed 

 for its reception. 



The collection is rich in Ascidiae Compositse, but although many 

 of them are new species, the great majority belong to well-known 

 genera. This can be accounted for by the fact clearly brought out 

 by the " Challenger " collection, that the Ascidise Compositae form 

 essentially a shallow-water group, the bulk of the collection having 

 been obtained close to land, or at localities, such as Kerguelen Island 

 and Port Jackson, where the shore fauna was investigated. A few 

 Compound Ascidians were, however, obtained from great depths, such 

 as 1,600, 2,050, and 2,900 fathoms, but they show few notable 

 morphological pecuharities. Perhaps the form most worthy of special 

 mention is Pharyngodictyon mirabile, in which the branchial sac is in the 

 curious simplified condition found in Culeolus amongst Simple 

 Ascidians. The horizontal distribution of the group is very wide, 

 representatives being found in all the great oceans and in almost all 

 latitudes. 



Among the Ascidiae Simplices, the most important new 

 forms constitute a small group of pedunculated Cynthiidae, apparently 

 confined to deep water, and characterised by several striking pecu- 

 liarities. They are more nearly allied to Boltenia than to any other 

 previously known genus, and have been placed in two closely related 

 new genera Culeolus and Fungnlus, the former containing seven 

 species and the latter one. Their most important morphological 

 feature is the very remarkable condition of the branchial sac, which 

 is simplified, apparently, by the total absence of the system of fine 

 interstigmatic vessels ; the result being that the large meshes formed 

 by the intersection of the transverse vessels, and the longitudinal bars, 



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