Manchester Memoirs, Vol. Iviii. {\g\^^. No. \. 5 



In every case the gills were removed immediately 

 after death and placed in a fixing solution of the following 

 composition : — 



90 parts of 70% alcohol. 

 7 „ 5% formalin. 



3 „ glacial acetic acid. 



They were left to harden for two or three days and 

 then embedded, and cut into sections, which were ulti- 

 mately stained with haematoxylin or brazilin. 



Microscopical examination of the Gills. 



The gills of Ligia, as in all Isopoda, are formed by 

 the modification of the abdominal appendages, and appear 

 as five pairs of white leaf-like structures upon the ventral 

 surface of the body. 



Each gill consists of a stout stalk, or peduncle, which 

 bears two broad, leaf-like lamellae, the endopodite and 

 exopodite. (P/. /., Fig^ i.) 



They are very similar in external appearance, although 

 the exopodite is slightly stouter and more opaque than 

 the endopodite ; in a transverse section, however, we see 

 that there is a considerable structural difference. 



The outer lamella {PI. /., Fig. 3.), which is slightly 

 larger than the itmer, consists of loose cellular tissue, with 

 nurnerous small nuclei, which stain deeply ; through this 

 tissue runs a well-defined and elaborate system of blood 

 vessels, and the whole structure is surrounded by a wide 

 hypodermal layer, and bounded by a thin cuticle. 



The inner lamella (/V. /., Fig. 2.), on the contrary, 

 contains no such definite system of blood vessels, but 

 consists chiefly of a broad, cytoplasmic la}'er of tissue, 

 containing numerous large nuclei, and seeming to be of a 



