366 
THE VOYAGE OF H.M.S. CHALLENGER, 
The preceding Table shows — first, that the Challenger Expedition obtained Compound 
Ascidians in all of the seven great areas into which the seas of the globe have been 
divided ; and, secondly, that comparatively few species were found in the Pacific Oceans. 
This is somewhat surprising, since more species of Simple Ascidians were collected in the 
South Pacific area than in any of the other regions.^ 
The Botr}dlid8e appear to be almost entirely confined to the North Atlantic, the only 
exceptions — according to the Challenger investigations — being the two species and a 
variety of Botrylloides which were obtained at or near the Philippine Islands. 
The Distomidse are distributed throughout all the oceanic areas with the exception of 
the North Pacific, and the genus Colella is represented in at least four of them, the 
Southern Ocean, the seas of the Malay Archipelago, the South Pacific, and the seas of 
South America. 
The great family Polyclinidae is also found in all the regions except the North Pacific ; 
more species are found in the ’Southern Ocean than elsewhere. Some of the larger 
genera, such as Polyclinum, Aplidium, Amaroucium, and Psammaplidium, have a very 
wide range. 
The Didemnidse occur in all the seven areas, the single Compound Ascidian {Lepto- 
clinum japonicum) found irs the North Pacific being a species of this family. The genus 
Leptoclinum (the largest genus in the Challenger Collection) is represented in all the 
regions, but is more abundant in the North and South Atlantic' than elsewhere. 
The Challenger Diplosomidae occur in the South Atlantic and in the Malay region. 
The family was previously known from the North Atlantic area. The Coelocormidse are 
only known from the South American region. 
The family Polystyelidse has a wide range. It was previously known from the North 
Atlantic area, and the Challenger investigations have shown that it is also represented in 
the South Atlantic, the Southern Ocean, the Malay seas, and the South American region. 
No members of the family have yet been discovered in the Pacific Ocean. 
Probably the most important conclusion to be drawn from the table is the wide 
distribution of most of the families and genera. 
In the following table, the last illustrating the geographical distribution of the 
Ascidim Composite, the occurrence of the different genera and species according to the 
latitude is shown in both northern and southern hemispheres. A + means merely that 
the species opposite which it is placed was found by the Challenger Expedition some- 
where between the limits of latitude which the column represents. Hence it may indicate 
more than one occurrence of the same species. 
1 See Part I. of this Eeport (vol. vi., 1882), p. 262. 
I 
