SEA-FISHE.TflES LABORATORY. 293 



examination showed, however, that the tumour was 

 situated behind the anus, and had nothing to do with this 

 opening. The tumours are not smooth, but appear to 

 consist of a mass of small spherical bodies rather less than 

 lmm. in diameter, and lying closely in contact with each 

 other. The skin covering the tumour is continuous with 

 that covering the body, and is pigmented in very much 

 the same way. Further examination showed, in fact, 

 that the tumour was a mass of Lymphocystis individuals. 

 In the same fishes there were other, but much smaller, 

 tumours containing the same sporozoan. In another 

 flounder, caught at the same time and in the same place, 

 there was a large tumour projecting from the body wall 

 on the blind side immediately over the anterior extremity 

 of the ovary. This tumour was so very like a portion 

 of the ovary that it was only by dissection and micro- 

 scopical examination that one could be convinced that the 

 body wall had not been ruptured in some way, and that 

 the ovary had grown through the opening. The tumour 

 was, however, connected to the body wall only by a pedicle 

 of tough connective tissue containing blood vessels. 

 Sections were made and stained, and it was then seen that 

 it was Lymphocystis with which we had to do. 



One of the specimens, with an anal tumour, was then 

 dissected, and text-figure 9 represents the relation of the 

 tumour to the surrounding structures. It lies quite clear 

 from the anus, and between the latter and the beginning 

 of the anal fin. On cutting it open its nucleus was seen 

 to be formed by a stout bone projecting through the 

 ventral body margin into the centre of the tumour. 



This bone is the hypertrophied ventral extremity of 

 the " anal spine." In all Pleuronectid fishes the posterior 

 wall of the body cavity is bounded by a large and strong 

 bone which curves round anteriorly from the roof of the 



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