The Common Liver Entozoon of Cattle. 119 



wards from either side, and meet together in the middle line. 

 The canals in question convey the yelk-granules., which are 

 formed in this curious set of organs, specially developed for 

 their secretion in the flukes. The terminal portion of the male 

 reproductive apparatus (fig. 6) is not unlike that of the Am- 

 phistome, the vasa defer entia uniting to form a sac, which 

 is lodged within a sheath-like pouch ; the latter embracing the 

 lower part of the spirally protruded intromittent organ. The 

 testes, instead of displaying the simple lobular character seen 

 in the Amphistome, are split up, as it were, into tortuous bands, 

 the two glandular masses together occupying the centre of the 

 body. According to Blanchard, the glands are intimately 

 blended with one another, and he also recognises the existence 

 of a third duct, which he represents as connected with the 

 shorter vas deferens. Be that as it may, the extent and com- 

 plication of these organs are sufficiently calculated to excite 

 astonishment -, whilst, at the same time, they afford a very fair 

 criterion of the reproductive powers enjoyed by this group of 

 animals. The eggs are a trifle larger than those of the Am- 

 phistome, the chorion or shell being of a yellow-brown colour 

 (fig. 7), and provided with a lid to facilitate the escape of the 

 enclosed ciliated embryo. The nervous system consists of two 

 cerebral lobes, one on either side of the oral cavity, and of a 

 series of feebly developed ganglia, connected to the former by 

 continuous filaments (fig. 4). Only two or three pairs of 

 ganglia have as yet been indicated, but the filaments have 

 been traced on either side of the body, to within a short dis- 

 tance of the caudal extremity. Kuchenmeister altogether 

 denies the existence of a nervous system in the fluke ; but he is 

 obviously unacquainted with the original discoveries of Mehlis 

 and the subsequent descriptions of Otto and Blanchard. 



Turn we now to the consideration of the habits of Fasciola 

 .Tiepatica, which, in so far as they relate to the excitation of the 

 liver disease in sheep, acquire the highest practical importance. 

 Intelligent cattle-breeders, agriculturists, and veterinarians 

 have all along observed that the rot, as this disease is called, is 

 particularly prevalent after long continued wet weather, and 

 more especially so if there have been a succession of wet 

 seasons : and from this circumstance they have very naturally 

 inferred that the humidity of the atmosphere, coupled with a 

 moist condition of the soil, forms the sole cause of the malady. 

 Co-ordinating with these facts, it has likewise been noticed that 

 the flocks grazing in low pastures and marshy districts are 

 much more liable to the invasion of this endemic disease than 

 are those pasturing on higher and drier grounds ; a noteworthy 

 exception occurring in the case of those flocks feeding in the 

 salt-water marshes of our eastern shores. The latter circum- 



