2 
Transactions of the 
TMonthly Microscopical 
L Journal, July 1, 1869. 
(Plate XYIII., Figs. 4, 5) ; or, by hardening the papillae in chromic 
acid, sections may be made showing the relations of the parts in situ. 
Fig. 8 represents such a section. 
The calyx (Fig. 4) is perforated by about 300 minute pores, 
each pore being surrounded by a nipple-like projection, which is 
surmounted by from three to eight minute setae (Fig. 6). The 
whole membrane of the calyx becomes thickened towards the apex, 
where it has a faint, yellow tint ; it is near the apex that the 
nipple-like projections and their setae are best seen, indeed a casual 
observer might overlook their presence entirely at the upper portion 
of the calyx. 
The calyx itself is marked by faint reticulations, and its margin 
is deeply crenated. These are the only indications of structure 
which it presents, and these seem to point to its being a fibrous 
membrane, especially as two sets of muscular fibres arise from the 
crenations of its margin. 
These muscular fibres are, first, a set from the muscular coat of 
the rectum, and, secondly, a layer of converging fibres which cover 
the whole base of the papilla to within a very short distance of its 
centre, and which apparently end in the edge of the membrane 
forming the boundary of the central cavity, although from the 
extreme transparency of this membrane it is nearly impossible to 
be certain of their insertion (Fig. 2). 
Each papilla is supplied with air by a large tracheal vessel from 
the last abdominal spiracle, which divides into several — generally 
five or six — large trunks before entering the papilla. The tracheas 
of the papilla may be divided into two sets as soon as they enter 
the base of the organ ; first, from twenty to thirty radiating lateral 
branches which run to the edge of the base (Fig. 7), and then pass 
over the outer surface of the glandular structure to the apex of 
the cone, giving off numerous branches, which anastomose freely, 
and form a fine reticulation around the gland cells, the larger 
branches running directly towards the central cavity, and forming 
loops by anastomosing with other similar vessels (Fig. 8). 
The second set are the terminations of the main tracheae : after 
giving off the lateral branches these run directly into the central 
cavity, where they become tortuous, and anastomose with each 
other, giving off comparatively few small vessels in proportion to 
their size, and forming a network which fills the central cavity, but 
none of their branches pierce its investing membrane anywhere. 
Fig. 5 represents the central cavity with its tracheae, with a small 
portion of the lateral branches and their terminations amongst the 
glandular structure. 
Each papilla receives two or three nerve filaments from one of 
a pair of nerves given off at the termination of the ventral cord, 
which are distributed to the muscular coat of the rectum ; a few 
