42 WILLIAM A. HASWELL. 
the anterior and posterior ends of the gizzard, is found to be 
a specialised part of the visceral system of nerves, becoming 
continuous, both in front and behind, with the ordinary nerves 
of that system. 
It remains to be mentioned that a layer of material similar 
to that which forms the main part of the core of the fibre is 
found also on the outer surface, and that processes from the 
ganglion-cells and its offshoots penetrate right through 
between the bundles of fibrils to enter this investing layer. 
It will be at once recognised that we have in these striated 
fibres of the gizzard of Syllis corruscans, structures of 
precisely the same character as the striated muscular fibres of 
the Arthropoda, the only differences of importance being in 
the mode of innervation, and in the arrangement of the undif- 
ferentiated protoplasm in relation to the muscle-substance. 
But the elements of the fibre are on a much larger scale than 
in the muscle of the Arthropoda, and what is only seen with 
difficulty in the latter, and by the use of the highest powers, 
can be seen very readily here, and with the use of only mode- 
rately high objectives. This is, therefore, a very favorable 
case for the examination of the minute structure, and the 
study of it seems to lead, as above indicated, to that view of 
the structure of compound striated fibres advocated by 
Retzius,! Bremer,’ Melland,®? C. F. Marshall,‘ and others; 
the only point of importance in which there seems to me 
reason for dissenting from that view, being with reference to 
the relations of the transverse networks to the fibrils. 
An important question which suggests itself when one is 
studying the structure of this peculiar striated muscular tissue 
1 « Zur Kenntniss der quergestreiften Muskelfaser,” ‘ Biologische Unter- 
suchungen ” (1881), ‘ Hofmann u. Schwalbe’s Jabresbericht’ (1882). 
2 “ Ueber die Muskelspindeln nebst Bemerkungen tiber Structur Neubil- 
dung u. Innervation der quergestreiften Muskelfaser,” ‘ Arch. f. Mikro. Anat.,’ 
xxii Bd. (1883). 
3 A Simplified View of Striated Muscle,” ‘Quart. Journ. Micr. Sci.’ 
(1885). 
4 «On the Structure and Distribution of Striped and Unstriped Muscle in 
the Animal Kingdom,” ‘ Quart. Journ. Micr. Sci.,’ xxviii (1887), 
