STUDIES OX THE ECTOPAHASITIC TREMATODES OF JAPAN. l^\ 



be regarded as a cliitiiiised portion (^f the investing mem- 

 brane. This view Avil], as Avill be seen afterwards, unify the oritrin 

 of the chitinous hook>; and rods that are found in various parts 

 of the body. 



The connective-tissue and chitinous penis of Monocotijle seem to 

 me to afford a starting point fov another type of copulatory organs, 

 that of the penis of Diclidopltora and Calicotijlc. In the latter genus 

 (PI. XIX, fig. 11) the bulbous penis, or as it may be called the biilbiis 

 coimlatorius^\ is a kidney-shaped mass of fibrous connective tissue 

 around the terminal portion of the vas deferens, before it is con- 

 tinued into the tabular chitinous penis. The latter is essentially 

 similar to tliat of Monocotijlc, and is enclosed in the genital atrium 

 which has here been reduced to a mere sheath for the chitinous penis. 

 The hulhiis copulatorins may be regarded as a farther differentia- 

 tion in a different direction of such penis as that of Monocotijle, in 

 consequence of which it has been almost completely separated from the 

 surrounding tissue. The only difterence is that in Monocoti/le it pro- 

 jects into the genital atrium, while in Calicotijlc it does not, and is 

 therefore traversed by the vas deferens. The connective-tissue penis of 

 DicUdopliom (PL XI, fig. 4) is essentially similar in structure — histo- 

 logical details and the shape not considered — to that of Calico- 

 tijlc. The chitinous penis is, however, replaced by the hooks already 

 described. These are also, in my opinion, formed by the local transforma- 

 tion of the lininii; membrane of the çrenital atrium, and are therefore 

 homologous in a broad sense to the chitinous ])3nis of Calicotijlc and 

 Monocotijlc. Unlike, however, what occurs iji tliese genera the lining 

 membrane has in Diclldophora not been raised and prolonged into a 

 tabular form and the whole then changed int(^ a chitinous substance, 

 but it has been raised at some particular points into the particuhu- 



1). Braun — W^ürmei'. p. 475. 



