508 



ZOOLOGY 





channels and containing gland-cells, which will be referred to 

 presently. 



According to their point of origin, the gills are divisible into 

 three sets first, podobra ncliice or foot-gills, springing from the 

 epipodites of the thoracic appendages, from which they are only 



FJC. 40-2. Respiratory organs of Astacus fluviatilis. In A the gill-covi 

 ' the gills undisturbed; in JJ the pi" are removed and the outer orthrol 



turned down, oj., antennule ; '(.,., antrim;i : abi.\ tirst ;,//..,.. srcond 



inner arthn< nathite ; 



11 13, pleurobmndiiie ; 



. 713, podobranchs ; p>. 1, first pi- 

 r Huxley.) 



partially separable ; SOCOIK^, <trtli.mlmincli'' f< ' <">r joint-gills, 



ing from the articular' incinbianes connectin the 



appendages with the trunk; and thirdly, pl&u 



gills, spi-ino-ing from the lateral walls of the th)hix, ;\bo\c il 



attachment of th<- a])[)cndagcs. ' It is infernxl fr(,ni tin- study 



othr !i< i s, that a tv]ical thoracic segment bcuis four 



one pod<>-. two anlii-o-, and one pleurobrancbia. 1 ',ut in Pofamobia 



;' \val 



