6 Stewart, Branchial Lamellae of Ligia oceanica. 



plasmodial nature, as no definite cell-structure could be 

 made out in any of the sections. 



This tissue surrounds a central lumen, which appears 

 filled with very loose, colourless, and faintly defined cellu- 

 lar tissue ; the whole structure, as in the exopodite, is 

 bounded by a definite cuticle. 



In every case the outer lamella extends considerably 

 below the inner one. 



The effect of the changed environment produces very 

 diverse effects upon the gill structure. 



Upon examination of a transverse section of the gills 

 of specimens from the first collection, which had been 

 immersed in sea-water, no definite change was observed, 

 but in the case of Ligias from the second collection a 

 gradual change was seen to have taken place, the endo- 

 podite being distinctly affected, while the exopodite 

 remained more or less unaltered. 



In a transverse section of the gill of a specimen kept 

 for four days in sea-water, it was seen that the soft 

 spongy tissue of the endopodite had become stringy or 

 striated, and numerous fine strands or threads of proto- 

 plasm were stretched across the lumen of the lamella. 

 {PI. /., Fig 4.) 



In the case of a specimen which had survived for a 

 week in sea-water, it was seen that the protoplasm of the 

 endopodite had become somewhat swollen and diffuse ; 

 the obliteration of the lumen had been carried further, by 

 the spreading out of fine protoplasmic strands. 



In another section of the gill of the same specimen 

 (/*/. 7/., Figs. I. and 2.), the cytoplasm was seen to be very 

 diffuse and swollen, only retaining its original form around 

 the scattered nuclei ; the lumen had completely dis- 

 appeared in places, and was only represented by one or 

 two disconnected spaces, crossed by the thread-like fibres. 



