THE EARTHWORM 277 



matozoa at any given time, otherwise there would be opposing currents. 

 The worms are so placed that the 9th segment of each is opposite the 

 32nd (1st clitellar) of its mate, then the thickened clitellum forms a bar- 

 rier past which no flow of seminal fluid can take place." 



'The long genital setae in the 'tubercula pubertatis' ( ) 



of the clitellum, and of segments 10 to 15, are probably used, the former 

 to liberate the coupon from its seat of origin, and the latter series to 

 hold the coc6on off the ventral surface in the region of the oviducal 

 openings and those of the spermathecae, and thus allow ova and sper- 

 matophores to pass into the cocoon as it passes forwards. These special- 

 ized setae replace those of ordinary form as the worm reaches maturity. 

 The eggs do not pass out of the oviduct till near the end of the act of 

 mating. Each of the two worms forms a cocoon, and slips out of it 

 backwards, passing it forward over its head. The cocoon being elastic 

 closes its two open ends as soon as the body of the worm is withdrawn, 

 and becomes more or less lemon-shaped, its bulging center being occu- 

 pied by about four eggs, spermatozoa and albuminous material produced 

 by the so-called capsulogenous glands, which may be seen on the ventral 

 side of some of the segments in front of the clitellum. The cocoons, at 

 first white but soon becoming yellow, are left in the earth, and as a rule 

 only one of the contained eggs produces a young worm. The size of the 

 cocoons differs in the various species, those of L. terrestris are from 

 6 to 8 mm. long by 4 to 6 mm. broad, of Eisenia foetida from 4 to 6 

 mm. long by 2 to 3 mm. broad. There is some doubt as to the precise 

 function of the spermathecae. It seems certain that the spermatozoa 

 contained in them are derived from some other worm. It is also the 

 case that these organs are full of spermatozoa prior to sexual union, and 

 are empty subsequent to that act, at any rate when cocoons are formed 

 and eggs deposited. Worms have been observed to separate without 

 producing cocoons, and though perhaps in some instances the separation 

 may have been due to disturbance caused by observation, yet there is 

 reason to think that two unions are necessary, one to fill the spermathe- 

 cae, and a second to form cocoons. In such a case it is probable that 

 each worm acts as a carrier of spermatozoa from its first to its second 

 mate, i. e., worm A gets its spermathecae filled by the spermatozoa of 

 B in the first union, and passes these spermatozoa to C in the second. 

 The actions are probably often reciprocal. According to Goehlich, while 

 spermatozoa are flowing from one worm to the spermathecae of the 

 other, there is given out from the spermathecae of the former a -small 

 quantity of mucus which hardens when it reaches the air : a second por- 

 tion of mucus containing a group of spermatozoa is then emitted, this 

 becomes attached to the first mass, and with it forms a spermatophore. 

 The whole spermatophore is attached to the body of the other worm 

 close to the clitellum. When the cocoon is made the spermatophores 

 are rubbed off into it as the animal withdraws itself. 



