88 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



breakdown, and the proliferation of the tissue of the 

 tumour into the surrounding structures. The details of 

 the capsulation are, therefore, of considerable interest. 



Fig". 1 of Plate II shows the place of apposition of 

 three small rounded tumours. No fine histological details 

 of the tissues of the tumour are represented, the latter 

 being indicated only by the fine stippling of the figure. 

 The boundaries of the tumours are formed by a fine, thin 

 layer of connective tissue, just a little denser than the 

 adjacent tissue. Between the tumours is a loose kind of 

 connective tissue containing some coarser fibres with some 

 bundles of muscle fibres, and round the tumours this tissue 

 seems only to become a little more compact and to be 

 roughly arranged in a concentric manner. 



Fig. 2 of Plate II represents quite a different kind of 

 boundary. Here the tumour is embedded in a mass of 

 adipose tissue which is situated near the base of the 

 ventral fin. Fig. 6 of Plate III represents the normal 

 appearance of the tissues in this region as seen under high 

 magnification. There are loose and irregularly-running 

 striped muscle fibres and small bundles of such, with 

 bundles of fibrous connective tissue, blood capillaries, 

 areolar connective tissue, and fat cells. The latter may 

 be relatively much more numerous than is represented in 

 this figure. In fig. 2 of Plate II the adipose tissue is 

 much denser, and here there appears to have taken place 

 a double progressive change : first, a development of 

 fibrous connective tissue among the fat cells, and then the 

 development of a typical, small-celled sarcoma along this 

 region of fibrosis. The locus of the sarcoma is represented 

 by the darkly stippled area, while the skeleton of 

 uniformly tinted material round the sarcomatous nodule 

 represents the area in which the process of fibrosis has 

 occurred. Under an apochromatic lens this fibrous bar- 



