PROBOSCIS OF SYLLIDEA 327 
of his own. He gives many details, more especially regarding 
the radial columns of striated muscle and the variations which 
they undergo in different families and genera. Since the 
publication of Malaquin’s valuable work there has not, so far 
as IT am aware, been any further contribution to the subject 
with the exception of the brief reference to it contained in 
a paper on the Exogoneae contributed by me to the Linnean 
Society (7). 
On approaching this subject anew, with a wider command of 
material, | have found that Malaquin’s account, excellent 
though it is, with many new observations, is yet not altogether 
correct in some respects, and leaves untouched several structural 
features that seem to be of some importance in connexion with 
the study of the proboscis as a mechanical system. 
The proventriculus is of cylindrical or sub-cylindrical form, 
usually with a small degree of lateral compression, and varies 
greatly in length in different members of the group. The 
surface is marked by a series of rings, an appearance which 
examination with a low power of the microscope shows to 
be due to the presence of annular fine lines and rows of dots. 
The fine lines correspond to annular bands of non-striated 
muscular fibres: the dots, which are frequently coloured in 
the living animal, are the outer ends of the cores of the radial 
columns of striated muscle. Along the dorsal side of the organ 
runs a longitudinal light or coloured line, the dorsal raphe, 
and a similar ventral raphe runs along the ventral 
side. 
A comparison of the pattern on the surface of the proven- 
triculus in representatives of different groups of the Syllidea 
reveals the occurrence of three main types. In one of these 
the annular lines alternate with the rows of dots. In a second 
the lines run through the dots. In the third type, which is the 
prevalent one in the Syllidae and in the Exogoneae, 
while the lines perforate the dots in all the lateral regions, 
they leave that position in the neighbourhood of the raphes, 
and pass to the latter in the intervals between the rows of dots. 
These three types of pattern arrangement mean respectively : 
