Anatomical structure of Aspidogaster conchicola. 523 



surface of the vagina to the left aud of the sinus genitalis to the 

 right. All the way, between penis sack and ductus is a fine paren- 

 chyma. The walls of the ductus are provided with strong inner 

 circular and outer longitudinal muscle fibres which, by their own 

 contraction, can force the mixture of sperm and secretion forwards 

 through the first series of folds into the barrel-like space (Fig. 9 CO) 

 between it and the second , outermost series. This forms a sort of 

 measuring apparatus which is then thrust forwards and as it is ex- 

 truded it is gradually reversed or turned inside out, beginning at the 

 most anterior end. By the time the reversal has reached the outer 

 row of folds there is already to some extent an intrusion into the 

 female organ ; and then by the continuation of the process the pressure 

 from behind as well as the reversal in front cause a throwing open 

 of the anterior folds, while the posterior are pressed close together 

 by their own musculature, contraction of the penis sack as well as 

 by the drawing forward of the latter and its crumpling by the paren- 

 chyma muscles. The filling parenchyma between duct and penis sack, 

 notwithstanding that it is not a watery fluid as stated by Voeltzkow, 

 can by its plasticity fulfill the same function that he attributed to it. 

 In the non -distended state the inner coatings of this part of the 

 ductus ejaculatorius, the intromittent organ (cirrus, penis), fall into 

 longitudinal ridges and furrows or circular folds, the former being 

 generally characteristic of the portion between the two circles of 

 papillae, the latter posterior to the last circle, but they may both be 

 present combined. The rings of papillae, also, which are only foldings 

 and fleshy ingrowths of the wall, may not be placed at right angles 

 to the direction of the lumen but running obliquely. The papillae 

 may vary in size and shape. 



Female organs. The ovary (Fig. 16, 11) lies a little anterior 

 to the testis but distinctly to the right of the middle line of the body. 

 It begins as a large oval mass with the large end of the oval turned 

 towards the genital sinus and the small end continuing into a tapering 

 tube which makes a sharp bend back along the inner side of the 

 main portion. If straightened out it would be recognized as a blindly 

 ending tube but widening considerably as it passes towards the blind 

 end where the eggs originate. The bending of the tube upon itself 

 produces a greater concentration of the organ. The whole lies turned 

 over on the side with the smaller portion left and more posterior. 

 When this has reached about the same length as the larger part it 

 makes a sharp turn obliquely backwards for an equal distance where 



Zool. Jahrb. IX. Abth. f. Morph, 35 



