78 SIDNEY F. HARMER. 
Fig. 1 (Pl. 7) gives two views of an extremely young 
colony of L. verrucaria. The colony is attached by means 
of a circular disc, whose diameter is ‘16 mm. The disc is 
formed, as Barrois has shown, by the calcification of the body- 
wall of the fixed larva. It gives off a calcareous tube which 
lies nearly horizontally, and ends in an open! mouth, whose 
diameter is ‘18 mm. On looking down into this mouth (Fig. 1, 8), 
it is seen that the cavity is divided by a septum which appears 
triradiate in end view. The septum does not in any part 
reach the margin of the aperture of the tube, while proximally 
it passes into the lower wall of the tube in such a way that the 
cavity of the disc is continuous with the part marked 1, and is 
entirely cut off from 2 and 3. 
A curious point may now be noticed. About. half the 
colonies of L. verrucaria may be described as “ right- 
handed,” and about half as “left-handed,” and this will 
become intelligible from a consideration of the woodcut (Fig. 1). 
Fic. 1.—Lichenopora verrucaria; diagram to explain the difference 
between “right-handed” and “left-handed” colonies. The growing 
margin of the colonies is omitted. I, IJ, and ILI are supposed to be 
seen from above, as in PI. 7, fig. 2. (For explanation, see text.) 
1 The mouth appears open (as in later stages) because it is uncalcified. 
The delicate layer of cells which stretches across it, and can readily be 
demonstrated in sections, disappears in the dried colony. 
