244 s. GOTO, 



evaginatei, and the spines serve to assist the act of copulation. 



After what have been said above I believe it is hardly necessary 

 to point out that the description of the "Cirrus" by Lorenz'Mn 

 Axine helones seems to me not to correspond to the actual relation of 

 things. I also venture to believe that what has been described by the 

 same writer as the male genital opening in Microcotijle mormyri is in 

 reality the opening of the genital atrium, and the assumed female pore 

 to be the opening of the uterus not to the exterior but into the genital 

 atrium. 



The spines that are present on the internal surface of the genital 

 atrium in Microcotyle and Axine I shall call atrial spines to distinguish 

 them from the penis spines or lioohs of Octocotyle and Diclidoplwra 

 and from the tubular chitinous penis of Calicotyle and Monocotyle. 



10. General Considerations and Comparison of Results. 



I .shall now add, partly by way of recapitulation, some general 

 considerations; and in the first place I shall discuss — 



1. The Nature of those prismatic, refractive Fibres which constitute the 

 Wall of the Suckers of Axine, Microcotyle, Octocotyle, Diclidophora, Hexa- 

 cotyle and Onchocotyle. These fibres have been spoken of by most writers 

 simply as muscular fibres; the only exception being, so far as I know, 

 Wright and Macallum, who say,^^ "Instead of the substance of 

 the sucker being foi'med of muscular fibres disposed in three directions, 

 and capable of modifying the shape of the cavity, as in the distomes, 

 it is not possessed of contractility in Sphyranura (and probably in 

 Polystomum), and is formed of prismatic fibres, rather of a supportive 

 than of a muscular character, arranged perpendicularly between the 

 concave and convex limiting membranes of the sucker." My observa- 



1). Lorenz — I. c. pp. 14 & 25. 



2). Wright & Macallum— i. c. p. 12. 



