LIFE HISTORY OF TEE LIVER-FLUKE. Ill 



counted; they vary in length from -025 — 0-35 mm.; each has 

 a very small nucleus, 0"00o mm. in diameter. The cilia are of 

 the same length ("012 mm.) over the whole of the surface, but 

 on the cells of the anterior ring they are more numerous, and 

 hence more conspicuous. This first row is composed of four 

 or sometimes five cells, arranged round the papilla, and these 

 are thicker than the other cells belonging to the same layer, 

 often forming ear-like projections at the side of the embryo, 

 and resembling epaulets. The second ring contains five or six 

 cells, the next two rows, each four, as a rule, whilst the last 

 ring is formed by two cells only. In the last two rings the 

 cells are of greater length than in the others. Seen in a 

 surface view the cells of this outer layer are polygonal and 

 sometimes hexagonal. They overlap one another at their 

 edges, and it is probably owing to this fact that the outlines 

 appear double in silver nitrate preparations. In the small 

 number of examples possessing six rows of cells, the second 

 and third rows are formed by smfillor cells. 



Beneath the ciliated cells the body wall is formed. by a 

 granular layer, the cellular nature of which is not easily made 

 out. In favorable preparations, however, nucleated cells can 

 be seen slightly projecting on the inner surface. In the outer 

 parts of the layer are situated both transverse and longitudinal 

 muscle-fibres. The longitudinal are more feebly developed than 

 the transverse, and are only seen with difficulty. The double 

 eye-spot belongs to this deeper layer ; it has been figured as 

 having a form of the sign of multiplication. This, however, is 

 not the case, for it is really double, and has commonly the form 

 of two crescentic masses of dark pigment, placed with their 

 convex sides turned towards each other, and in contact near 

 the anterior horns. On closer examination it is seen that each 

 eye-spot is composed of a cell in which the pigment is arranged 

 at one side in a crescent, the hollow of which is filled up by 

 refractive material which will act as a rudimentary lens. The 

 body wall also contains numerous yellowish refractive granules, 

 especially just behind the eye-spots, and to it belong the two 

 ciliated funnel-shaped spaces of the excretory system. These 



