<62 AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



excretion, for they are closely connected with the blood-vessels, 

 resemble excretory cells in their granular character, and are known 

 to break down into the ccelom, the materials thus formed being 

 very probably got rid of by the nephridia. 



The urine, as the excreted substances may be collectively 

 termed, passes down the nephridia by the action of the cilia, 

 and collecting in the dilated muscular section is expelled by its 

 contraction. 



6. Reproductive Organs (Fig. 19). The Earthworm is herma- 

 phrodite, and its sexual organs vary much in size, according 

 to the time of year, being largest in the summer, which is the 

 breeding-season. The segments in which they are placed are 

 anterior to the clitellum. Their colour is white, and they lie 

 below and at the sides of the gut, in its oesophageal region. 



(1) Male Organs. There are two pairs of minute flattened 

 spermaries (T), produced into finger-like processes behind. These 

 are attached, near the nerve-cord, to the back of the septa forming 

 the anterior boundaries of segments 10 and 11. In the sexually 

 mature state they project into the cavities of the seminal reser- 

 voirs. The most conspicuous parts of the male apparatus are the 

 vesiculce seminales, three pairs of large white pouches which may 

 completely overlap the oesophagus, and are situated in segments 

 9-12. The anterior pair (A) lie in segment 9, and are united 

 into a median seminal reservoir (B) in segment 10. This also 

 receives the middle (C) pair of vesiculse situated in segment 11, 

 while the posterior vesicular are situated in segment 12, and unite 

 into a similar reservoir in segment 1 1 . Projecting into the floor 

 of each reservoir is a pair of large plicated seminal funnels (S F) 

 turned towards the testes. From each funnel a delicate tube, the 

 vas efferens, proceeds, which, after forming a coil, takes a backward 

 course. The two vasa efferentia on each side unite together in 

 segment 12 into a straight tube, the s])ermidud (VD), which 

 passes back through segments 13 and 14 to open by the male 

 pore on segment 1 5, just external to the ventral setae. 



The spermary may be regarded as a thickened and specialized 

 part of the epithelium lining the body-cavity. It is made up 

 of numerous germinal-cells which, as mother-sperm-cells, pass into 

 the vesicula3 seminales, the cavities of which are traversed by 

 numerous strands of connective tissue. In the interstices between 

 these the mother-sperm-cells undergo repeated division or seg- 



