188 
W. BALDWIN SPENCER. 
apart from each other, not closely applied upon the dorsal 
surface of the alimentary canal as in Gammarus, whilst also 
their openings into the gut are lateral and not dorsal. The 
definite shape of the hind gut may be noticed in passing, as 
also the fact that it possesses a distinct cuticular lining beset 
throughout the greater part of its course with little processes, 
though towards the anterior end these disappear, and the cuti- 
cular lining itself becomes very thin indeed. 
With regard to the tubes their walls are cellular in nature 
just as in Gammarus, and by focussing under a high power 
each cell may be seen to have its inner end which faces into 
the lumen of the tube rounded, whilst its outer end is roughly 
hexagonal in outline. The most interesting fact, however, is 
that, in certain specimens, as in the one figured, these tubes 
were found to contain very definite concretions. If a great 
number of animals be examined there will be found perhaps 
one or two of a light greenish colour, and through the cuticle 
of which may be seen, on either side posteriorly, a white streak 
indicating the position of these tubules. In a specimen of this 
description concretions will most likely be found filling the 
whole cavity of the tube. 
The concretions are of various sizes and arranged as in the 
figure, smaller ones being placed between each larger one, the 
latter, apparently consisting of several of the former united 
together in some manner. In no case could any sign of a 
concretion be observed either within or between the cells of 
the tubes themselves. 
In one or two instances they have been met with in an 
animal of a dark reddish-brown colour, differing in tint from 
the usual greenish brown, though in this case the concretions 
were only small ones and did not exist in the proximal, but 
only in the distal half of the tube. 
Though as yet I have not been able to obtain definite proof, 
still, judging from the condition of the cuticle in the two kinds 
of specimens in which only these concretions have been found 
(the first mentioned especially being clearly distinguishable 
from the normal Talitrus), it may not appear unjustifiable to 
