vn PRACTICAL DIRECTIONS 395 



clean thoroughly. Examine the joints and make out the 

 relations of the endophragmal system (p. 392), looking 

 something like a lattice-girder. 



3. Examine your preparation of the eye once more under 

 the microscope and notice the part where the section passes 

 through the outer wall of the eye-stalk, so as to make out 

 the microscopic structure of the integument and exo- 

 skeleton, which, apart from the calcification, is similar in 

 all parts. Notice the epiderm, and the thick, laminated 

 chitinous cuticle, the superficial layer of which is uncalcified 

 throughout. 



G. Dissection from the Side. 



Cut through the carapace 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. 389). 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 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 antennary 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. 93. 



Once more carefully follow out the structure and rela- 

 tions of all the organs exposed, and sketch your dissection. 



