36 WILLIAM A. HASWELL. 
state for microscopic examination. So far as my observations 
on this species extend, they agree entirely with Emery’s de- 
scription. The tissue is at once recognisable in my specimen, 
when the body-cavity is opened from above and the alimentary 
canal removed, as a silvery-looking delicate cord running 
along the middle ventral line, and giving off at regular in- 
tervals series of radiating branches which pass in amongst the 
ordinary muscular tissue of the body-wall and parapodia. 
The cord and its branches are remarkable in the preserved 
specimen for their brittleness, almost resembling in this 
respect and in their appearance delicate threads of spun glass. 
Treatment with Heidenhain’s hematoxylin brings out the 
alternate zigzag bands of stainable and unstainable material, 
but does not reveal any trace of transverse membranes. 
In Syllis the gizzard has the form of a cask or a short 
cylinder. The striated muscular fibres which make up the 
greater part of the wall of this organ are arranged in a 
radiating manner in a series of transverse (annular) rows. 
In Syllis corruscans (figs. 1—3) the fibres are of, com- 
paratively speaking, large dimensions, being ‘5 mm. in length 
and ‘16 mm. in greatest breadth. In shape each fibre may be 
described broadly as cylindrical; but the ends are hexagonal, 
the outer end is broader than the inner, and there is a longi- 
tudinal fissure along the greater part of the length of each 
side; the ends, which are comparatively broad surfaces at 
right angles to the long axis of the fibre, are firmly implanted 
into thin strata of non-striated muscle. The muscular sub- 
stance composing the walls of this cylindrical fibre is formed 
of fibrils! about ‘(003 mm. in diameter, arranged parallel with 
one another and each running the whole length of the fibre. 
It is made up of alternating zones or segments of singly 
1 The term fibril is used here in all cases to designate those elements of 
compound striated muscle, the bundles of which, united together by continous 
transverse networks, constitute the fibres; the fibrils in turn may show 
indications of being made up of a number of much smaller elements, the 
fibrillules. To avoid confusion the elements of the transverse and longitu- 
dinal networks are called threads or filaments, 
