4 Stewart, Branchial Lamellae of Ligia oceanica. 



that the effect of sea-water is more harmful than that of 

 fresh, but as the quality of sea-water used in this experi- 

 ment was very unsatisfactory, the contradictory result in 

 this case may, I think, be fairly disregarded. 



On examination of the gills of the latter specimens, 

 they exhibited no such radical change as in the experiment 

 with fresh water — death in the second case being probably 

 due to the unhealthy composition of the water, rather 

 than to asphyxiation from prolonged immersion. 



The remainder of the Ligias, which were kept among 

 a quantity of moist Fuais, in a tin receptacle, lived quite 

 healthily for ten days. 



The second collection of specimens was received from 

 Swanage on Saturday, December 7th, and these again 

 were large forms, in excellent condition, many being egg- 

 bearing females ; of these, four were taken and placed in 

 fresh water, and four more were placed in a vessel of clean, 

 fresh sea water. 



On the following Monday, of the forms in fresh water, 

 two were found to be already dead, and the other two 

 were in a dying condition ; in every case the gill lamellae 

 were considerably distorted and swollen. 



The Ligias in sea water, when observed after 24 hours' 

 immersion, were all quite healthy, and displayed consider- 

 able activity ; they were kept in the same vessel and 

 lived for nine days, the water being kept continually 

 changed, and death eventually seemed due to insufficient 

 food rather than to the external conditions. 



On a superficial examination the gills did not exhibit 

 any abnormal features. 



Several more Ligias from the same batch were also 

 placed in a second vessel of sea-water, and lived for six 

 days, without appearing to be in any way affected by the 

 immersion. 



