* 



DISTOMA HEPATICUM. 253 



Whether ciliated lappets occur in this excretory organ in our 

 Distomum, I cannot say, as the Dist. hepaticum is too massive 

 and thick in the body. It is well known that they are deficient 

 in one species and present in another, and they appear as a 

 general rule to possess no great functional value. 



Organs of reproduction. — 1. The female sexual organs lie more 

 towards the ventral surface of the animal, and consist of a 

 germ-stock with its efferent duct, two vitelligenes, a short ovi- 

 duct, a sac-like uterus, and a vagina. 



a. For a long time I could not quite make out the germ-stock 

 in our Distomum. I regard as this organ a round body which 

 lies behind the cordate point of union of the two vitelligenes in 

 the median line of the body, and a little way behind the last 

 convolutions of the uterine sac. This is the same structure that 

 others have taken for a testicle. In spite of all the trouble that 

 I have taken to unriddle the nature of this round body, I have only 

 succeeded in coming to an approximate understanding of it. I 

 sought in vain in this body for spermatozoids, which would have 

 rendered it a vesica seminalis interna. But as often as I isolated 

 it and examined it in this state, I could only detect in it, with 

 the highest magnifying powers, a great number of very clear, 

 oval, empty, capsular structures ; for which reason I have been 

 tempted to regard this organ as the germ-stock, but without 

 venturing to give this interpretation as the only correct one. 

 This structure at any rate opens into a common canal with the 

 efferent duct of the vitelligenes, in which true egg-structures 

 immediately make their appearance, and which at the same time 

 contains immense numbers of spermatozoids, which are agglome- 

 rated together in masses in the midst of and around the indi- 

 vidual eggs which are still transparent. From here onwards, the 

 union of the germinal vesicles and yelk-globules, as well as the 

 formation of the egg-shell, certainly goes forward. 



b. The vitelligenes (yelk-sacs) form two organs placed at the sides, 

 consisting of blind sacs, forming repeatedly branched, beautifully 

 dendritic or racemose figures, which reach anteriorly into the 

 level of the cirrhus, and posteriorly into the caudal extremity, 

 where they are only separated by the excretory organ, and thus 

 prevented from passing into each other in this close point of 

 contact. They collect on each side into a common and tolerably 

 strong stem, running parallel to the lateral margins of the 

 animal, from which, at about the point where the anterior third 



