PROBOSCIS OF SYLLIDEA 331 
As regards the cortex of the column. This consists of a bundle 
of fibrils among which penetrate branching processes from the 
protoplasmic core. Each column or fibre is characterized, 
except in the Exogoneae, by the presence of one (Ty po- 
syllis variegata, T. closterobranchia, T. trun- 
cata), or more ‘striations’. In all essentials these fibres 
resemble the striated fibres of Arthropods and Vertebrates. 
The fibrils of each are bound together by one or more transverse 
membranes (Krause’s membranes, telophragms) which pass 
through the fibrils, and, through the interfibrillar substance, 
bind all the fibrils intimately together. ‘The fibre itself is 
composed of alternating zones of singly and doubly refracting 
material, the telophragms passing through the latter. More- 
over, gold-chloride methods reveal systems of J-granules 
(sarcosomes) and transverse networks in the neighbourhood 
of the telophragms, exactly as is the case in the striated muscles 
of Arthropods and Vertebrates. 
At their outer and mner ends the fibrils of the striated 
muscular fibres are firmly fixed into the outer and inner 
fibrous membranes. 
Occupying much less bulk than the radial fibres are the 
annular bundles of non-striated fibres. The extent of this 
system, its relations and the part which it plays in the move- 
ments of the proventriculus, have not hitherto received adequate 
attention. Malaquin, a little misled by his idea of a system 
of transverse septa separating the annular rows of muscle- 
columns from one another, pays little heed to these bundles. 
He says in his account of the proventriculus of the Autolytea 
(p. 217), ‘Comme nous aurons l'occasion de le voir plus loin 
pour d’autres types, il est des points du diaphragme ot les 
fibrilles, s’arrangeant en faisceaux, ont tout a fait l’apparence 
de fibres musculaires, et on peut croire alors que ce tissu con- 
jonctif fibrillaire passe au tissu musculaire proprement dit. 
Nous reviendrons sur ce point & propos d’un autre type’. 
" Mesophragms and Q-granules I have not hitherto succeeded in detecting, 
except somewhat doubtfully in the case of Syllis (Ty posyllis) varie- 
gata. 
