///. ANNELIDA: CH^TOPODA. 



315 



presence of numerous glands, forming a clitellum (fig. 274), which 

 secretes the egg cocoons. The clitellum also functions in copula- 

 tion, secreting bands \vhich hold the animals together so that 

 the sperm from one passes into the receptaculum seminis of the 

 other. After impregation the eggs are usually enclosed in 

 cocoons. 



Sub Order I. LIMICOLA (Microdrili. ) Mostly fresh-water forms. 

 The TUBIFICID.E, in consequence of the red blood, when present in large 

 numbers color the bottom red. They quickly retract into the tubes which 



FIG. 285. Aulophorus vagus, in tube of Pectinatella statoblasts. (After Leidy.) 



they form in the mud. Tubifex* Petoscolex ; Clitellio irroratus* common 

 on our seashores. The NAIDID^E are transparent forms living on water 

 plants which reproduce asexually throughout nearly the whole year. 



\r-vd 



cti 



FIG. 286. Sexual organs of Lumbricus herculeus (after Vogt et Jung); the seminal 

 vesicles of the right side cut away, hm, ventral nerve cord; foZ, bi\ lateral and ven- 

 tral rows of setse; di, septa ; ftj, ft s , testes, enclosed in sperm reservoir; o, ovaries ; 

 ew, oviducts ; sbu, sperm reservoir ; sftj, 2 , 3 , sperm sacs (seminal vesicles) : *t 

 seminal receptacles; t,, t s , seminal funnels connected with the vasa deferentia; 

 to, funnels of oviducts; rd, vas def erens. 



Z>ero* and Aulophorus* have gills around the anus. ENCHYTILEIDJE ; 

 Distichopus, Pachydrilus. The DISCODRILIDJE (Bdellodrilus, Nyzobdella) 

 are parasitic. 



Sub Order II. TERRICOLA (Macrodrili). Here belong the terrestrial 

 forms, the earthworms, our species of moderate size, in the tropics large 



