PRACTICAL STUDY OF LUMBRICUS. Ill 



cut through the stomach-intestine, seize the fore part at the cut 

 with forceps and turn it forwards, gradually cutting away its 

 connection with fine scissors so as finally to expose the reproduc- 

 tive organs. The smaller parts must be sought out with a hand- 

 lens. Observe and sketch 



a. Testes and seminal vesicle. 



l>. Seminal receptacles. 



c. Sperm-ducts follow them out. 



d. Ovaries. Remove with fine forceps, mount, and exam- 



ine with the microscope. 



e. Oviducts. 



f. Examine with high powers spermatozoa from, the semi- 



nal vesicles or seminal receptacles. 

 E. Histology. (See Appendix.) 



1. Preliminary study. With a sharp razor make thick sec- 

 tions (i.e., about ^ inch) of a preserved specimen through the 

 following regions, viz., pharynx, oesophagus, crop or gizzard, 

 clitellum, and at two or three points of the region behind the 

 clitellum. Place the sections for an hour or more in strong 

 glycerine, mount in glycerine and study with low power (1-inch 

 obj.). Make out and sketch the general arrangement of parts, 

 and as many details as possible. Observe especially the setse, 

 the muscles, and the alimentary canal. Preserve these slides for 

 comparison with the following : 



2. Make thin cross-sections by the paraffin-method through 

 the same regions studied in (1). Observe with low power 



a. Layers of the body-wall. 



lj. Layers of the alimentary wall, typhlosole. 



c. Position of blood-vessels, nerve-chain, nephridia, setae, 



and other organs. 



d. Interpret in the sections the appearances of the dis- 



sepiments, often very puzzling on account of their 

 oblique position. 



e. Observe the stained corpuscles of the coelomic blood- 



often very clear and beautiful. 



f. Study with high powers the structure of- 



a. Body-wall. 

 ft. Alimentary wall. 



y. Nerve-ganglion. Trace nerves out into muscles. 

 d. Nephridia, reproductive organs, etc. 

 g. Compare with the preceding a longitudinal section. 



