374 
THE VOYAGE OF H.M.S. CHALLENGEE. 
From this table it is a simple matter to determine the range in depth of any 
particular genus, e.g .\ — 
Botrylloides . extends from shallow water to 530 fathoms. 
Colella . ,, 5 to 245 fathoms. 
Polyclinum . ,, 3 to 600 ,, 
The seven families of Ascidise Composite are found to have the following limits : — 
The Botryllidse range from the shore to 530 fathoms. 
The Distomidm ,, ,, 450 ■ ,, 
The Polyclinidse ,, ,, 1600 ,, 
The Didemnidse ,, ,, 600 ,, 
The Diplosomidae are confined to shallow water. 
The Coelocormidse have only been found at a depth of 600 fathoms. 
The Polystyelidse range from 5 to 70 fathoms. 
Hence it appears that, with the exception of the Coelocormidse, only known from a 
single specimen of Ccelocormus huxleyi obtained off the east coast of South America, 
there is no family peculiar to deep water ; each of the others contains some species 
ranging from quite shallow water downwards. Four of the families, the Botryllidse, 
the Polyclinidse, the Didemnidse, and the Ccelocormidse, are represented in the abyssal 
zone,’^ while one other, the Distomidse, is found at very considerable depths. The 
remaining two, the Diplosomidse and the Polystyelidse, are only known from depths 
of less than 100 fathoms. 
The Polyclinidse is the only family which extends into water of over 1000 fathoms, 
and it is only represented in such depths by one species [Pharyngodictyon mirahile). 
If this species were placed in an independent family, then the limit in depth of the 
Polyclinidse, as now known, would be 600 fathoms. 
In the Botrylhdse, although only one species [Botrylloides fulgurale) is abyssal, three 
genera are represented at considerable depths, viz., Botrylloides at 530 fathoms, and 
Sarcohotrylloides and Polycyclus both at 363 fathoms. 
In the Distomidse there is no peculiarly deep-water genus, but four species occur 
at depths of over 100 fathoms, viz., Colella murrayi, 120 fathoms, Colella ramulosa, 
245 fathoms, [f)clava, 450 fathoms, and Cystodytes draschii, 400 fathoms. 
The other species are all shallow-water forms. ' 
In the Polyclinidse, Pharyngodictyon is the only deep-water genus, but five species 
of the family, belonging to four distinct genera, extend into the abyssal zone. The 
other members of the family are nearly all confined to shallow water. 
Depths of 500 fathoms and upwards. 
