476 EDGAR J. ALLEN. 
III. Sensory ExLements. 
These are nerve elements in which the cell lies outside the 
ganglionic cord. 
M. 
Up to the present I have only been able to obtain satis- 
factory staining of such elements in lobster embryos in the 
abdomen. If the ganglionic cord in the thorax be cut across 
at any point behind the csophagus, numerous longitudinal 
fibres take up the methylene blue, and many of these continue 
to stain until, on turning the embryo over, they may be seen 
to pass into the abdomen. In some preparations some such 
fibres are seen to pass out at the lateral nerves of the abdo- 
minal ganglia, and may be traced backwards and upwards to 
the dorsal surface of the abdomen, where they end in cells 
similar to those described by Lenhossék! and Retzius? in the 
earthworm, and by Retzius* in Polychetes and Molluscs. 
These cells vary somewhat in shape. Two of them are repre- 
sented in fig. 10. The cell itself is generally spindle-shaped, 
the distal end either running out and ending in a sharp fibre 
(fig. 10, 6), or being flattened out as in fig. 10 (a). In other 
cases the distal end of the cell appears rounded, as in the lower 
cell of fig. 11, but this may be due to incomplete staining. 
The fibre arising from the proximal end of the cell, which 
lies on the dorsal surface of the abdomen, is moderately fine, 
and as previously stated passes forwards and downwards to the 
nerve cord. The cell generally lies vertically over the gan- 
glion behind that into which the fibre enters (fig. 11). Within 
the ganglion the fibre bifurcates, forming a Y-shaped figure, 
one arm of which passes forwards and the other backwards. 
As to the endings of these fibres, I regret that I can at present 
* Lenhossék, “ Ursprung, Verlauf, und Endigung der sensibeln nerven- 
fasern bei Lumbricus,” ‘ Arch. mikr. Anat.,’ 39, 1892. 
? Retzius, “Das nervensystem der Lumbricinen,” ‘ Biol. Untersuch.,’ 
neue Folge iii, 1892. 
5 Retzius, “Das nervensystem der Lumbricinen,” ‘ Biol, Untersuch.,’ 
neue Folge, iv, 1892. 
