SEA-FISHERIES LABORATORY. 89 



work is seen to be a dense felt-work of very fine inter- 

 lacing fibres without any obvious nuclei. In Mallorjr 

 preparations it is seen to be greatly altered in places, 

 becoming almost uniform in structure. There is no 

 distinct boundary between it and the adjacent fat cells, 

 and some of the latter seem to be actually embedded in the 

 felt-work. Apparently it is the result of the progressive 

 development of the connective tissue stroma still existing 

 between the fully formed fat cells. Then along this 

 region of fibrosis the cells of the sarcoma appear to be 

 proliferating, so that we have a series of changes in the 

 original normal tissues in this part of the fish. These 

 are (1) the replacement of the areolar connective tissue by 

 adipose tissue, producing the structure represented at the 

 marginal parts of the figure; (2) the fibrosis of this 

 adipose tissue, that is, a progressive development of the 

 stroma that remained after fat-formation had attained its 

 maximum; and (3) the multiplication of the connective 

 tissue cells remaining in the stroma, and the prolifera- 

 tion of those cells along the regions of fibrosis as a small- 

 round-celled sarcoma. The alteration in the fibrosed 

 tissues we may regard as due to the influence of the fully- 

 developed sarcoma. In the fresh condition the latter 

 was pink in colour, and as there were already small groups 

 of melanin granules scattered throughout it, we may, 

 perhaps, regard the pink colour as indicating the first 

 stages in the process of melanisation of the tumour. 



Figs. 1 and 2 of Plate II represent, therefore, the 

 contrasted conditions of capsulated and non-capsulated 

 tumours. Figs. 3 to 7 of the same plate represent 

 conditions where tumours already distinctly capsulated 

 are actively proliferating by the breakdown, in places, of 

 the capsules. Fig. 3 is a low-power drawing. The 

 stippled area represents the locus of the tumour, which 



