
ON A DEEP SEA TOW-NET, ETC. 109 
is suspended by a loop of wire, which is passed over the 
loop (j.) before it is fixed in its notch. The latter is 
similarly suspended to the loop (e.). When this second 
net 1s opened by its first messenger the corresponding 
messenger just below it is liberated as soon as 7. slips out 
of its notch and runs down to open the first tow-net. 
In the same manner the shutting of the second net also 
closes the first. 
ADVANTAGES AND DRAWBACKS. 
The apparatus just described seems to me to present the 
following advantages over any which has hitherto been 
described :— 
1. It will work equally well at any depth. 
2. The times of opening and shutting are entirely under 
the control of the operator. 
3. It will work either on a special rope or on one which 
is being used with a dredge or trawl. 
4. A number of nets can be worked simultaneously on 
the same rope. 
' Tt cannot be denied, however, that it also has certain 
drawbacks. ‘The first, and to my mind the most serious, 
is that any foreign body becoming attached to the rope, 
such for example as a piece of Alga or the trailing threads 
of a Siphonophore or Medusa, would check the descent of 
the messengers, and thus prevent the working of the net. 
This accident has never as yet occurred in my experience, 
but its possibility is obvious. 
Again, when the speed of towing is at all high compared 
with the weight of the apparatus, the inclination of the 
towing rope to the horizontal is very small, especially 
near its lower extremity, and the friction of ‘the water 
being considerable the descent of the messengers is slow, 
