SEA-FISHERIES LABORATORY. 297 



were quite free from the parasites occurring on the skin. 

 The gills were also free and apparently quite healthy. 



Fig. 19 represents a general view of a part of the skin 

 which has been stained with carmine and cleared in clove 

 oil. The parasitic structures are mostly covered by the 

 scales. Each is covered over by a thin fold of epidermis. 

 Usually they are situated beneath the posterior margin 

 of the scales under the fold of epidermis which is 

 reflected over the latter. Sometimes they are apparently 

 quite free from the surface of the skin and can easily be 

 detached by the point of a scalpel, but in such cases they 

 are attached by a delicate pedicel of epidermic tissue. 

 In sections of the skin taken in a transverse plane they 

 can be seen lying beneath the tips of the spines of the 

 scales, which are then cut transversely. 



In section each of the parasitic bodies is almost 

 certainly a unicellular structure. It is surrounded by a 

 fairly thick, apparently structureless capsule, which 

 stains with difficulty and is, therefore, more easily seen 

 in the unstained preparations. Within is the cell body, 

 containing near the centre an irregularly-shaped included 

 portion surrounded by a differentiated portion of the 

 matrix, which may represent a nuclear membrane. Within 

 this is what may be called a nucleus. There is a matrix 

 of finely granular substance in which are usually two or 

 more rounded karyosomes. 



The cell substance outside the nucleus stains rather 

 more darkly than that within because of the presence of 

 numerous granules. It shows no clearly marked cortical 

 zone, but round the periphery are a number of reticular 

 structures, very irregular in shape and size, and usually 

 surrounding a portion of cell substance which stains more 

 lightly than that in which the reticula are imbedded. 

 Each of these reticula appears to consist of innumerable 



