The Rot in Sheep. 



same thing again and again, for it has always been our object to 

 obtain the entozoon alive for our investigations and dissections. 



That a strong ccsophagean sphincter is required can be easily 

 understood, when it is remembered that on the creature having 

 forced itself into the smaller ramifications of the biliary ducts, 

 the pressure exerted on its body by the peristaltic action of the 

 ducts must at times be very considerable, and that this pressure 

 might otherwise drive the alimentary matter out of the digestive 

 organs. Indeed, in dead flukes the sphincter is still so firmly 

 closed that, by pressure between two plates of glass, the alimen- 

 tary materials can be easily driven backwards and forwards and 

 made to press against the lower part of the oesophagus, without 

 being driven through it into the mouth. The free passage of the 

 contents of the digestive organs in either direction shows, how- 

 ever, that every facility is given for the oral sucker to act either 

 as an inlet or outlet to the digestive system. 



Generative Organs. — The reproductive system is without doubt 

 by far the most interesting portion of the organisation of the 

 distoma, but at the same time it is the most complex, and hence 

 difficult of investigation. This chiefly arises from the circum- 

 stance that the entozoon is hermaphroditic or bi-sexile, and as a 

 necessary consequence the male and female organs are inter- 

 mingled to some extent, while their naturally large development 

 requires their occupancy of a considerable portion of the body of 

 the creature. In the illustration {fig. 7) inserted overleaf, the 

 generative organs are represented apart from any others — an 

 arrangement which will materially assist our description. We 

 shall first explain the several peculiarities of the female organs, 

 and follow with those of the male. 



Female Organs : the Vitelligenes, or yelk-forming organs (a a, 

 Jig. 7, page 44). These structures occupy the margins of the body- 

 on either side, extending from about opposite the inferior portion 

 of the ventral sucker to the extreme end of the distoma. The yelk 

 sacs are clustered around minute tubes in the form of branches, 

 somewhat like currants upon their footstalks, giving a beautiful 

 dendritic character to the whole arrangement. The stems of these 

 tubes are in turn connected with two larger ducts, b />, which take 

 more or less in wavy course parallel with the margins of the 

 entozoon. These ducts receive the contents of the smaller tubes, 

 which they transmit by two horizontal branches, c c, to an ovoid 

 body situated in the centre of the creature at about its upper 

 third. This body has been by some helminthologists called the 

 "germ stock." In some specimens of distoma in our collection 

 a third branch is seen to proceed from the yelk sacs towards the 

 '? germ stock," joining the main horizontal duct before it reaches 

 that body. 



