after fertilization undergo total segmentation. There is a primi- 

 tive band much as in insects, and the adult form is attained before 

 tlif ;iniiu:il is hatched. There is no metamorphosis. So with the 

 earthworms. Kowalevsky studied the mode of development of 

 two species. As nothing has heretofore been known of the life- 

 history of so common a creature we will delay a moment to learn 

 the results of the Russian naturalist's observation. The eggs of 

 the European Lumbricus agricola were laid while the worm was in 

 confinement in January and^ February. They were laid in nu- 



though usually only three or four embryos were found in a capsule. 

 The egg-capsules of Lumbricus rubellus were found in dung. 



not to correspond to the gastrula condition of other worms, al- 



there are two primitive germ-lanielhc. Later in emluyoiiic life, 

 a primitive band like that of insects (which will be described 

 farther on), rests on the outside of the yolk, as in the leach (Hirudo 

 medicinalis). Finally, the form of the earthworm is attained 

 before it breaks through the egg-shell, and it hatches without un- 

 dergoing a metamorphosis, in a condition differing but slightly 

 from that of the adult worm so familiar to us, the body being pro- 



We now come to the sea worms, or Annelides, in which there 

 are external gills and often a complicated locomotive apparatus, 

 consisting of fleshy oar-like projections from the body, and strong 

 bristles. They have free-swimming larva?, which by a complicated 

 niet:iniorph<»-i>, coinparaMe with that of the Nemertian worms, 

 attain the adult worm-condition. 



A singular type is Phoronis, which lives in a membranous tube 

 attached to rocks, and recalls strikingly the appearance of a Poly- 

 zoan, as it has a true lophophore and the inte-t me open- externally 

 near the mouth. It is in fact a connecting link between the Annel- 

 ides and the Polyzoa. Its life-history as told by Metschnikotf is 

 nearly identical with that of Sipunculus. 



We will now in a fragmentary way study the mode of develop- 

 ment of certain typical Annelides, beginning with the lower forms. 



