216 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



A and its tow-net at about 10 fathoms caught nearly 

 twice as much material as the same two nets (13) worked 

 at about 20 fathoms. 



The further point is that in each case the tow-net 

 retained the Diatoms, the Dinofiagellates, the minute 

 larval forms and the smaller Copepoda which had escaped 

 the shear-net, while the latter caught more of the larger 

 organisms, such as Medusae, Sagitta, Microniscus, and the 

 large Copepod Calanus. The number of organisms in the 

 tow-net in each case is enormously greater, but those in 

 the shear-net bulk larger on account of their individual 

 size. 



Taking the last item on the lists as an example, the 

 obvious explanation of the numbers would be that there 

 were more Ascidian eggs at 10 fathoms than at 20, and 

 therefore tow-net A caught more than tow-net B ; no 

 doubt both shear-nets being so much larger caught still 

 more, but the majority of the eggs passed through the 

 wide meshes, and only a very few (25) were retained 

 accidentally in each case, probably through being 

 entangled in the appendages of larger Crustacea or 

 through the blocking up of some of the meshes. 



The Surface Nets. 



The two ordinary open tow-nets with a mouth 

 diameter of 14^ inches, and made of silk No. 9, with 

 94 threads to the inch, were towed side by side on the 

 surface of the sea about 50 feet behind the ship for fifteen 

 minutes on each occasion. In the great majority of cases 

 it may be certain that their catch was limited to the upper 

 two feet of the sea ; and yet notwithstanding the 

 uniformity of the conditions the results w r ere in many 

 cases very different. The following list shows the bulk of 

 the catches on the various occasions when the two nets were 



