38o THE CRAYFISH chap, vi 



wall of the eye-stalk, so as to make out the microscopic structure of the 

 integument and exoskeleton, which apart from the calcification, is similar 

 in all parts. Notice the epidenn, and the thick, laminated, chitinous 

 cuticle, the superficial layer of which.is uncalcified throughout. 



G. Dissection from the Side. 



Cut through the carajiace on the dorsal side as before, but be careful 

 to keep your cut very slightly to one side — say the left— of the 

 middle line, and when the pericardium is exposed, inject the arteries 

 through the heart as before (p. 374). Then remove the gill-cover of the 

 same side, and examine the gills once more. 



Remove and examine again all the appendages of the same side, and 

 then carefully continue cutting longitudinally through the exoskeleton, 

 both dorsally and ventrally, close to the middle line, taking care you do 

 not injure any median organs. Remove the entire exoskeleton of 

 this side, as well as the dorsal and ventral muscles, cutting through the 

 latter in the median line very carefully. 



After your dissection has been pinned down under water, the green- 

 gland, digestive gland, and gonad of the same side should also be 

 removed, and the gizzard cut open. Then tidy up the dissection, 

 which will now be reduced to a longitudinal section like that represented 

 in Fig. 86. 



Once more carefully follow out the structure and relations of all the 

 organs exposed, and sketch your dissection, 



