BY WILLIAM A. HASWELL. 
1707 
fibres, the annular and the radial. The only other class of 
“ Worms” in which simple striated fibres appear to occur is in 
certain Rotatoria ; but these cases I have not had the opportunity 
of examining ; it is possible that they may be degenerate com- 
pound fibres. 
In connection with no group of animals do we find a greater con- 
flict of statements regarding the muscular tissue than in the case 
of the Mollusca. Striated fibres have been described in the swim- 
ming lobes of the Pteropoda and Heteropoda, in the buccal mass 
of various Gastei’opoda (Leydig,'^ Schwalbe,! Marshall,! Harvey 
Gibson§), in the heart of various Mollusca (Leydig,^ Dogiel, || 
Gibson§), in the retractor of the eyes of Helix (Gegenbaur^), the 
abductors of various Lamellibranchs (Schwalbe,! Wagener,^'^-' 
Marshall!), the abductor of the Pectinidse alone (Blanchard!!) 
while Pol!! has recently announced the opinion that ‘true striation’ 
does not occur in any Mollusc. I have not been able to go over 
more than a small portion of the ground covered by the literature 
of this part of the subject ; but the observations which I have 
been able to make have led me to a conclusion which may be 
said to be intermediate between the opinion expressed by 
Blanchard and that expressed by Pol. 
* “ Lehrbuch der Histologic. ” 
t L.c. 
: L.c. 
§ “ Anatomy and Physiology of Patella vulgata, Part I. Anatomy,” 
‘ Trans. Roy. Soc. Edin,’ Vol. XXXII. (1886). 
II “ Die Muskeln und Nerven des Herzens bei einigen Mollusken. ” 
‘ Archiv f. mikro. Anat.’ XIV. Bd. (1877). 
*T “ Die Entwickelungsgeschichte der Landgastropoden. ” ‘ Zeitschr. f. 
wiss. Zool.’ III. Bd. (1851). 
** “ Ueber die Muskelfaser der Evertebraten.” ‘ Archiv von Reichert 
und du Boia-Reymond, ’ 1863. 
t+ “ A propos des muscles stride des Mollusques Lamellibranches.” ‘ Bull. 
Soc. Zool. France,’ 1888. Also, “ Sur la structures des muscles stride des 
Mollusques Lamellibranches.” ‘ Bull. Soc. Zool. France,’ 1888. 
XX “ Sur la structure microscopi(iue des muscles <les Mollusques.” 
‘ Comptes Rendus,’ CVI. (1888). 
