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case of the lateral series (see Text-fig. 4). The constrictor muscles of the 
pharynx, which are disposed alternately with the individual elements 
of the series of dilator muscles, form a succession of slender bands 
connecting the angles formed by the six longitudinal folds of the 
pharyngeal wall, each complete member of the series thus presenting, 
in transverse sections through the pharynx, the appearance of a 
triangular figure with truncated angles. 
The muscles of the oesophagus and stomach are represented by the 
layer of muscle fibres which enters into the formation of the walls of 
these organs, and sufficient reference has been made to their structure 
and arrangement in the general description of these organs. 
The anal muscles, as previously shown (Part II, p. 241), are short 
strands which connect the upper extremity of the anal canal with the 
lateral margins of the anal valves. 
(cl) The Muscles of the Genitalia. 
The muscles of the genitalia are divided into two groups— (a) those 
which connect some part of the genital tract with the body wall or 
endosternite, and ( b) the muscles which form the muscular layers in the 
walls of the genital canals. 
The extrinsic muscles are the superior and the inferior genital 
muscles (see Part II, Plate XVI, figs. 3 and 4, m. gen.) which are 
attached to the terminal section of the genital canal but show a slight 
difference in their relations in the two sexes. 
In the male, the superior genital muscles take their origin from the 
ventral surface of the endosternite as a cluster of slender strands which 
pass almost vertically downwards and are inserted into the proximal 
part of the dorsal wall of the ductus ejaculatorius. In the female, they 
originate in a similar manner, and find their insertion in a corresponding 
situation on the dorsal wall of the terminal section of the vagina. 
The inferior genital muscles arise from the ventral body wall in 
the post-genital area, and pass obliquely forwards to be inserted into 
the ventral wall of the ductus ejaculatorius in the male, and into the 
posterior lip of the genital orifice in the female. Further reference is 
made to these muscles in the description of the genital organs. 
In a preceding section of this paper dealing with the body-muscles, 
brief reference was made to a pair of muscles which are closely connected 
with the genital organs. These are the clorso-genital muscles (in. gen'.) 
which take their origin from a pair of discs situated on the middle of 
