314 On the Young Stages of a few Annelids. 



longer so much out of proportion as to give the larva the 

 hammer shape it possessed before ; the part of the disk anterior 

 to the vibratile ring has somewhat elongated; the mouth (m) 

 when seen from the ventral side, Fig. 8, appears quadrangular 

 with rounded edges ; it is situated close behind the anterior vi- 

 bratile chord, and edged on the posterior extremity with a row 

 of large pigment cells. 



We now come to a series of changes plainly showing the 

 passage from the stage represented by Loven in his Fig. 5 to 

 that of his Fig. 6. Although the body of the young worm is much 

 elongated, the number of rings, Fig. 9, has not greatly 

 increased ; they are further apart, and there is a tendency in 

 the stomach, which occupies nearly the whole width of the 

 body, to become folded, so as to correspond to the articula- 

 tions ; the anterior part of the head has greatly elongated, and 

 the general appearance of the young worm reminds us some- 

 what of the larva of Sipunculus nudus figured by Keferstein 

 and Ehlers. The vibratile rings are greatly reduced, the an- 

 tennae have slightly increased in length, and the head of the 

 worm presents a certain resemblance to a Nereid or some 

 allied form. The swelling of the posterior extremity has also 

 been reduced, the anal vibratile chord scarcely projects beyond 

 the line of the body. The pigment spots of the rings have 

 diminished in number but slightly increased in size ; and the 

 brilliant row of spots of the oral and anal rings is beginning 

 to fade, the vibratile cilia are losing much of their activity, 

 and the little worm, though still capable of swimming freely 

 about, and often caught at this stage with the dip net, moves 

 quite slowly and has gradually lost, with the extension of the 

 posterior part of the body, the rapidity of motion it enjoyed in 

 the earlier stages (Figs. 3, 4). When kept in confinement 

 they are often found at the bottom of the vessel coiled up, 

 and when disturbed creep slowly away by undulations of 

 the body, assisted by the remnants of the vibratile rings. In 

 a somewhat more advanced stage, Fig. 10, the pigment spots 



