i8 94 .] THE BRITISH NATURALIST. 



277 



pseudopods on the 4th and 5th segments. The tail proper ends with a 

 .long conical brown tube, enlarged at the end with a point, and narrowed 

 towards the middle, and terminating in 6 long, strong bristles. 



The body is covered with minute hairs, plates, or specs, which are 

 very distinct on the tail portion, and the nth segment has a curious 

 branching, branchial filament. 



De Geer says the pupa lies on the top of the water for only four days, 

 and then rapidly changes into a small, slender, black midge, with two long 

 thread-like antennae, thin, erect, and hairy. The balancers are club- 

 shaped, and are rather long and flat. The wings are white and 

 transparent, with very small hairs on all the nervules. 



On the top of Plate XII. I give, as promised, two transverse sections 

 of this Dixa larva, cut by Professor Miall, F.R.S., showing the ventral 

 nerve-cord " d" under the intestinal canal, while beneath are the 

 hooklets of the false feet. A finely branched trachea runs on either 

 side of the intestine, shown at " c " in Figs. 1 and 2. 



Marine Form of Larval Trichoptera. 



We now come to the last of my curious Aquatic Larvae. This was 

 found in the open sea, off the mouth of the Ribble. There was a pretty 

 strong tide running up the estuary, and I was fishing with my bottle 

 and surface net off the end of St. Anne's Pier. Amongst my captures 

 was a curious lively little creature in a very transparent capsule or case, 

 not more than one-eighth of an inch in length. At first I thought it 

 was a minute form of crustacean, as some of the amphipods construct 

 cases or cells, and it was evidently quite at home in its salt-water 

 quarters. Its abdomen very much resembled a small hermit-crab's, 

 being swollen, nearly transparent, and very slightly segmented. But 

 when I had killed and mounted my little treasure, I feared that its 

 limbs, though arthropod, were not crustacean ; and so the puzzle went 

 on, for at that time I was quite ignorant that any marine caddis worms 

 were known. I sent photographs of my micro mount in several 

 directions, as it appears in Fig. 3, Plate XII., and at last one of the 

 assistants of Professor Herdman, F.R.S., of Liverpool, thought it 

 resembled some fresh water larvae which his father, Mr. Thos. Scott, 

 F.L S., had found in Loch Tay, and some of these he promised to send 

 me. These, when mounted, immediately gave me the key to the puzzle; 

 for while their likeness to my specimen was very marked in respect to 

 the head and the three pairs of legs, the segments of the abdomen 

 were now so plainly seen that "caddis fly larva" occured at once to my 

 mind. Plate XII., Fig. 4. 



But whoever heard of a pelagic caddis worm? and yet the tidal 

 current was running from the open sea. The only conclusion I can come 

 to is, that my specimen was hatched in brackish water, near the mouth 



