APPENDIX. 
415 
99). Examine the soft parts in a dish of water or of fifty per 
cent, alcohol. Note the mantle lobes, the gills, the foot, the 
mouth parts, etc. Cut open the body, and trace the digestive, 
nervous (Fig. 134), and the principal parts of the circulatory 
systems (Fig. 46). Harden specimens in alcohol, and make 
transverse sections through the body, and examine the sections 
again in dishes of fifty per cent, alcohol, tracing in this way 
the course taken by the digestive system (Fig. 78). 
Arthropoda.—( A ) Crustacea.— Use the Lobster or Crayfish. 
Study living specimens in jars of water. Examine the manner of 
walking and swimming ; of grasping food and chewing it; of 
defending themselves ; the motions of the antennary organs, the 
eyes, and the appendages of the abdomen. Note the segmented 
structure, the segments being grouped into well-defined regions 
forming the cephalo-thorax and the abdomen. Note the presence 
of a pair of appendages on each of the abdominal segments; 
the similarity of structure of all these appendages except the 
last, and the extreme specialization of this one. On the cephalo- 
thorax look for segments; note here also the arrangement of the 
appendages; remove them in order from one side, and trace the 
modification of the same fundamental plan of structure. Open 
one of the large claws and study the contained muscles. Note 
especially the arrangement and structure of the mouth parts, 
eyes, and antennary organs (Fig. 250). With a pair of strong 
shears cut through the “ shell ” along each side and remove the 
roof of the abdomen, thus exposing the muscles within, and the 
posterior part of the circulatory and digestive system. Note 
the arrangement of the muscles and blood-vessels. In the same 
manner remove the top of the cephalo-thorax, examining the 
chamber in which the gills lie and their arrangement. The 
heart and stomach will now be exposed, also the “ brain ” (Fig. 
70). Examine all these. Remove the digestive system, and, 
lying below it, find the ventral nerve chain. Look also for 
nerves running to the eyes. 
(B) Insecta.— The large Locust or Grasshopper will be use¬ 
ful to study the general characteristics of insects. It is difficult 
to keep living specimens confined for any great length of time, 
consequently the best observations of their habits must be made 
out-of-doors. Recently caught or alcoholic specimens may be 
used for studying the anatomy. Notice here, as in the Lobster 
and the Earthworm, that the body is segmented; but the seg- 
