268 ELEMENTARY BIOLOGY. [CHAP. 



I. The reproductive organs. (Cf. Sect. C. e.) Best ex- 

 amined in specimens captured during spring and summer. 

 i. Obtain the body of the largest worm possible (one 

 having a good clitellum). Open up the anterior 

 twenty segments along the dorsal middle line under 

 spirit (stretching the body to the utmost) and remove 

 the alimentary canal with care, leaving the mesen- 

 teric septa undisturbed. Look for 



a. The spermathecce, two pairs of small yellowish- 

 white globular bodies, attached to septa 9 10 

 and 10 ii. 



They are developed within the substance of the 

 septa referred to, and may project forwardly into 

 segments 9 and 10 or backwardly into 10 u. 



Their points of exit are invariable, and they may 

 conveniently be used as landmarks in dealing with 

 the remaining organs of the reproductive system. 



b. The seminal vesicles^ 3 4 pairs of soft whitish 

 organs attached to septa 9 10, 10 n and n -12. 

 They are internal to a. 



In Allolobophora there are four pairs, always dis- 

 tinct. In the sexually mature Lumbricus the 3 pairs 

 present unite with each other and their fellows of the 

 opposite side to form a highly conspicuous mass 

 lying beneath the alimentary canal. 



c. Remove the seminal vesicles of one side and ex- 

 amine the mouths of the vasa deferentia (ciliated 

 rosettes}. They are dead-white glairy structures, 

 lying near the middle line in segments 10 and n ; 

 when fully formed exceedingly conspicuous and 

 chalky looking. 



d. Trace back the ducts of c, on one side. Each per- 

 forates the septum behind it and becomes im- 



