SEHA-FISHERIES LABORATORY. 387 
(fig. 39). They consist essentially of two transverse 
ridges of tissue, very similar, histologically, to the palps, 
but without the grooves. 
These two ridges, however, are produced in certain 
places into prolongations, which, as well as the free edge 
of the lips generally, divide and re-divide into very small, 
short and swollen processes. In this way the hps come 
to have a dendritic appearance. There are two main 
prolongations of the upper lip with dendritic margins, 
situated one at each side near the origins of the labial 
palps. The lower hp has a very large median prolonga- 
tion which interlocks with those above, and lesser ones 
along the sides. It seems, therefore, that this develop- 
ment of the branched margins is for the purpose of closing 
over the mouth, leaving a channel which communicates 
at each side with the groove between the two labial palps. 
The margins of the lips are deeply pigmented with 
the same orange-yellow that is found on the palps, and 
also lining the oesophagus. 
The upper surface of the upper lip and the lower 
surface of the lower lp are bounded by a layer of 
epithelial cells, which are almost cubical in shape, and 
are crowded with pigment granules, especially near the 
surface. ‘his layer is continuous with the somewhat 
similar layer that covers the outer surfaces of the labial 
palps. The surfaces of the upper and lower lips, which 
face one another and are continuous with the grooved 
surfaces of the labial palps, are bounded by a layer of 
much elongated columnar cells, which contain no 
pigment, but bear numerous cilia. The structure between 
these two layers is loosely packed connective tissue, with 
numerous spaces containing blood corpuscles. A slightly 
‘denser layer immediately underlies the epidermis. 
The mouth itself (fig. 39, I.) is a transverse slit 
