BATIIYMETRICAL DISTEIBUTION. 



Some of tlie pelagic Tunicata in the Challenger collection are labelled as having 

 been obtained in nets sent down to as much as over two thousand fathoms. 

 But it is probably scarcely worth while recording these depths or drawing any 

 conclusions from them, because in the absence of any means of opening and closing 

 the mouth of the tow-net at will, so as to be able to collect from one particular 

 stratum of water, it must be a matter of uncertainty where the specimens obtained in 

 the net were really captured. 



In the case of Station 318, where a tow-net was attached to the trawl and let 

 down to a depth of 2040 fathoms, while another tow-net was used at the surface, 

 the contents of the net were found to be the same in the two cases, consisting of : — 



Several specimens of Doliolum chrc7iherrp , Krohn ; 

 and of Doliolum sp. (blastozooids). 



So we may conclude either that the surface forms go down to a considerable depth, or 

 that the deep tow-net captured its specimens on the way down or on the way up. 



Consequently, in the present state of our knowledge, the only deep-sea group 

 belonging to these Tunicata discussed in the present part of the Report is the family 

 Octacnemidse, including the genus Octacnemus, which is probably attached to the 

 bottom, and has only been found at the depths of 1070 and 2160 fathoms. 



