BY PROFESSOR AV. A. HASWELL. 499 



cyst of Cerca7'ia armata, also, nuclei are absent in the cuticle 

 according to Schwarze (12). 



The germinal epithelium (fig. 8) lines the whole interior of the 

 Sporocyst. In the greater part of its extent in a mature Sporo- 

 cyst it is a thin layer of flattened cells, most of which are stellate, 

 the processes of neighbouring cells anastomosing to form a net- 

 work. At the anterior and posterior ends it is thickened, the 

 thickening consisting of a layer of vertically elongated cells. At 

 its outer end each cell of these thickened regions terminates 

 in one or several very fine processes, which are clearly 

 traceable through the layer of muscle, and are seen to 

 be continuous with the vertical striations of the cuticle. At 

 its opposite free end each cell projects into the cavity of the 

 Sporocyst. In the living specimen globules were seen to be given 

 off occasionally from the inner ends of these cells, becoming free 

 in the interior of the cavity, and often becoming collected in 

 masses. These globules were swallowed by the more mature 

 Cercaripe, in the intestine of which considerable numbers of them 

 were nearly always to be detected. It might be supposed that 

 this phenomenon is not a natural one, but brought about by the 

 pressure to which the living Sporoc3^st is naturally subjected in 

 order that its structure may be examined. But such an explana- 

 tion cannot be entertained in view of the results obtained from 

 the examination of sections of specimens fixed by various reagents. 

 In such sections the epithelium has the appearance represented in 

 in fig. 8, the cells presenting a variety of stages in the process of 

 formation of the globules; and many of the latter are to be found 

 free in the cavity of the Sporocyst and in the intestine of the 

 Cercaria3. Among the globules in the latter position entire 

 nucleated cells are frequently to be observed. 



It thus appears to be almost certain that the germinal epithe- 

 lium has an important secondary function in providing nutriment 

 for the Cercarise with fully developed and functional digestive 

 canal. To nourish the many growing embryos which it contains, 

 the wall of the Sporocyst must absorb nutrient matter in large 

 quantity from the tissues of its host. This is taken in, un- 



