18 A MANUAL OF ZOOLOGY 



' -The excretory system is represented by a pair of 

 organs, nephridia, in each segment except the first three. 

 With the low power find the opening in the septum, and to 

 the outside. Are both ends of the nephrldlal organ in the 

 same segment? 



The reproductive system is represented by the seminal 

 vesicles, the testes, the ovaries, and the spermathecae. In 

 the segments 9 to 12 find the large pouch shaped boc(jfs 

 (seminal vesicles). How many pairs are there? Note aW^ 

 difference in size. Remove the roof of the median vesiclat 

 and find the testes Inside the vesicle. The sperm cells arei 

 shed into the vesicles in an immature stage and undergo 

 their maturation there. The tubes leading from the 

 vesicles unite to form the vas-deferens, whose opening is 

 on the thirteenth segment. Look in segment 13 near the 

 septum between that, and the 12th segment for small 

 rounded bodies, the ovaries. The oviducts pass through 

 the septum and ppen on the 14th segment. The sperma- 

 thecae, small globular , bodies, are found in the 9th and 

 10th segments. Study a live worm, noting all the move- 

 ments. Place some on a smooth surface and others on a 

 rough surface. Note any differences in their movements 

 on the different surfaces. Place some leaves on the sur- 

 face of the dirt in a box containing earthworms and leave 

 them several days. . Note from day to day any change in 

 the position of the leaves. Account for the same. 



PHYLUM ARTHROPODA 



Crustacea 

 Lobster or Crayfish. 

 The laboratory guide Is especially adapted to the lob- 

 ster, but will 'apply in general tgi. the crayfish. With 

 specimens beforfe you study the general shape. How does 

 it differ from anything studied before? ■ Note the head 

 covering, exoskeleton. LOok for bilateral symmetry. Why 

 is this animal called an .arthropod? Note that the body 

 proper is differentiated. How many distinct regions are 

 found? How does the ictilerior region, the.^ephalothorax, 

 differ from the posterior region, the abdomen? How many 

 segments are found in the abdomen? How are the seg- 

 ments joined? Is there any suggestion of a joint? If so. 



