202 
ROBERT SCHARFF. 
destroyed in cutting tlie section or by the action of the 
alcohol. 
Ehlers 1 does not give us much information as to the spikes 
on the body proper, and merely states that they are small 
cylindrical elevations truncated at their upper extremity. 
“ Their height is 0143 mm. and their diameter 0111 mm., and 
in their interior, chiefly at the base, lies the substance of the 
subcuticular layer.” The only other observer in whose writings 
I can find anything about these spikes is Horst. 2 He makes 
mention of the fact that the hypodermic cells form a continuous 
layer on the internal surface of the cuticle. The central part 
is said to contain a network of nucleated fibres. 
We now come to the consideration of those dermal organs 
about which there prevails a good deal of difference of opinion 
among the various writers. I am alluding to the papillose 
clusters of dermal processes at the posterior part of the body 
(fig. 4, p.) Even with a strong lens nothing but pretty con- 
siderable thickenings of the nature of warts can be made out. 
On examining the cuticle separately, however, groups of eleva- 
tions can easily be seen, in the centre of which a pore is to 
be found (fig. 9). The cuticle here appears to sink into small 
funnel-shaped pits. In reality, however, these pits are a 
number of extremely minute tubes, only visible under very 
high power. In a surface view their real nature might quite 
easily be mistaken, and it is probably this reason which induced 
Ehlers to describe them as pits. The general arrangement as 
seen by a low power is shown in Ehlers’ monograph on the 
genus Priapulus (pi. xxi, fig. 18) (see also my diagram, fig. 4). 
The main structure of the warts on which the small tubules 
stand is made up of modified hypodermic cells. These are 
elongated and filled with granulated contents (fig. 10). The 
cells differ considerably from those of any other part of the 
body in being packed closely together and in being of a much 
greater width. Figure 5 is an attempt to make these state- 
ments clearer by showing one of these organs in a longitudinal 
1 Ehlers, loc. cit., p. 225. 
3 Horst, loc. cit., p. 18. 
