348 LEWIS HEXRY GOUGH. 



Tlie muscles in the scolex are more complicated than those 

 iu the strobila, as their coarse is modified by the suckers^and 

 their requiremeiits (Liihe, 1894). The following systems of 

 muscles have been made out in connection with the suckers of 

 Avitellina centripunctata (Rivolta). 



Commencing at the apex of the scolex, and proceeding 

 towards the strobila, we meet : 



(1) A diagonal cross-system anterior to the terminal loops 

 of the excretory canals; it covers the entire anterior surface 

 of the scolex, passing from the front of the left ventral to 

 the front of the right dorsal sucker, and from the front of 

 the right ventral to the front of the left dorsal sucker. 



(2) A second diagonal cross system, composed of four 

 bundles of muscles, each consisting of only a few fibres, is 

 situated just posterior to the terminal loops of the ventral 

 canals ; it runs from sucker to sucker in such a way as to 

 connect — 



(a) The median face of the light ventral sucker with the 

 lateral face of the left dorsal sucker. 



(b) The lateral face of the right ventral sucker with the 

 median face of the left dorsal sucker. 



(c) The median face of the left ventral sucker with the 

 lateral face of the right dorsal sucker. 



(d) The lateral face of the left ventral sucker with the 

 median face of the right dorsal sucker. 



(3) An orthagonal cross-system, running dorso-ventral and 

 transversely, is situated just behind the second diagonal cross 

 system and between it and the great nerve commissures. It 

 connects : 



(a) The median faces of the two left suckers. 



(b) The median faces of the two right suckers. 



(c) The lateral faces of the two dorsal suckers. 



(d) The lateral faces of the two ventral suckers. 



(4) A second orthagonal cross-system is situated behind 

 the nerve commissure, near the base of the suckers. Its 

 insertions correspond to those of the previous orthagonal 

 system. 



