STUDIES OX THE ECTOPAKASITIO TRE.MAT«.»DES OF JAPAN. 



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finely librous. coinp:i(*r connective tissue (PI. X^'^T, i\<x. ,']). The 

 chitinous penis is t>iniil;u' to that of CnUeotiih', but is shorter ;in*l more 

 slender (PI. XVIT. tigs. \ & 2 ; PI. XA'III. h.o-s. 3 .<: 7). ;.n.l is 

 somewh.-'.t spiral. Tts h:(se is (lire<.-tly :ij)[)lie(l to the terininaiioii 

 of the vas deferens, and lies enclosed in the tubular cavitv of the 

 ])enis Avitli only its terminal |)ai't ])rojeetinii' iiito the î^'enital atianm 

 under the usual cii'cumstances. 



Tristoniinn and Epihdella — In these genera the chitinous penis 

 is entirely wanting, and in both, the ])enis is neai-Iy alike in structure as 

 well as in ])Osition relative to the other parts of the geriital organs. 

 Unlike all the genera liitherto described, the common genital 

 pore, or in some species the se])arate male and female openings, are 

 situated quite in tlie later;d part of the body, a little behind the left 

 anterior sucker. The penis is an elongated, hollow. sul)C<^niçal body 

 projecting for the greater part of its whole length into the genital 

 atrium. The basal pi^rtion of the penis is separated from the surround- 

 ing mesenchyma by a thin, dense layer of connective tissue which yiyid- 

 ly takes u]) the stain. This layer is, however, absent for a certain 

 extent at the yer}^ base of tlie ])enis, so that here the substance of the 

 penis is directly contiraious with the general mesenchyma of the l)ody 

 (PI. XXII, hg. '2). The cavity of the penis is tubular foi- the grea.ter 

 part of its length, luit at its base it is enlarged spherically :ind receives 

 the openings of the ])rostate glands. 



The substance of the penis is somewhat différent in histological 

 structure in different species; l)ut generally it consists of a loose, 

 reticulated, fibrous connective tissue (PI. XXII. fig. 4; 1^1. XXIV, fig. 

 1). In tliose s[)ecies the mesenchyma of which is more or less of a 

 syncytial nature, as TriM. siniuduin. the meshes of the connective tissue 

 are filled with a gramdar substance ; Init the fibrous element seems 

 always to pre])onderate in the penis (PI. XXII, hg. 4). 4^)wards the 



