568 APPENDIX 



Specimens of the Leech must be bought from a dealer. 



I. Note the movements of the worm in swimming and 



The Leech. looping. It is often difficult to induce it to feed. 



When it does so, it can be induced to relax its hold 



by salt sprinkled on its back, but the bleeding of the wound 



is sometimes difficult to stop. 



2. Note : in dorsal view, annuli, spots which mark the true 



segments, eyes, hinder sucker, anus ; in ventral view, oral 

 sucker, mouth, penis (thrust out), female opening, hinder 

 sucker (Fig. 150). 



3. Examine the mouth and remove a jaw (after 5). 



4. Pin the leech through the suckers, stretching well. Open it by 



a dorsal incision a little to one side of the middle line ; care- 

 fully dissect away the skin and pin it out. Wash. Note : 

 dorsal sinus, lateral vessels ; pharynx, crop, caeca, stomach, 

 intestine (Fig. 151); nephridia. 



5. Remove the alimentary canal. Note : nervous system ; 



nephridia ; generative organs (Fig. 150). 

 10. Examine a transverse section (Fig. 152). 

 Crayfish occur in streams in many parts of Britain, but are most 

 conveniently obtained from dealers. Bought specimens 

 The Crayfish, may be of the French species. 



I. In the living animal note movements of limbs in 



locomotion and feeding. With a pipette place carmine at 



the bases of the legs and note that it is sucked under the 



branchiostegite and drive out below the antenna. Cut away 



the branchiostegite above the jaws, and note the movement 



of the scaphognathite. 



Crayfish may be kept alive for a long time in running water. They 



should be killed with hot water, and may then be preserved in 70 per 



cent, alcohol. Preserved specimens are only of use for examination of 



external features and of the nervous system. 



2. Note : in dorsal view, cephalothorax, rostrum, cervical groove, 



branchiostegite, abdominal terga, telson ; eyes ; antennules, 

 antennae, scales of latter, great chela, walking legs, uropods 

 (Fig. 153) ; in ventral view, limbs (working with list on 

 p. 247, as individual jaws are difficult to identify for the 

 first time until they are removed) ; sterna (Fig. 154). 



3. Remove the telson. Note the sixth abdominal segment with 



its limbs. 



Remove the sixth abdominal segment and view the fifth 

 from behind. Note : tergum, sternum, pleura, limbs (Fig. 

 158). 



Remove the limbs of one side from behind forwards, 

 bringing away the podobranchise with the legs to which they 

 belong, arrange the limbs on a sheet of paper, and compare 

 with the figures on pp. 245-249, noting the parts of each. 

 Cut away the branchiostegite (Fig. 163) and count the gills. 



4. Cut away the median part of the carapace and of the abdominal 



terga. Note : heart, ostia ; ovary, or testes and vasa 

 deferentia ; " stomach," muscles running from it to carapace, 



