340 On the Young Stages of a few Annelids. 



plication of any systematic value; when a greater number 

 of Annelids have been studied, the dorsal cirri, as well as the 

 characters of the tentacles of the anterior part of the bodv, will 

 furnish us valuable additional guides for classification in rela- 

 tion to the rank of families and genera ; and as far as we can 

 make use of them they seem to coincide remarkably with the 

 generally received notions of superiority and inferiority of the 

 principal families, current among the most accurate investiga- 

 tors of Annelids. 



EXPLANATION OF LETTERING AND FIGURES. 



v. anterior vibratile ring. t. tentacles. 



v'. anal vibratile ring. y. concretion capsules. 



m. mouth. a. anus. 



e. eye specks. r 5 . 5th ring in Polydora. 



o. oesophagus. r. first ring, the rings are counted 



from here. 



s. stomach. g. glands of Polydora. 

 c. intestine. 



Fig. 1. Young Planakia angulata, with distinct articulations seen 

 from above. 



Fig. 2. Somewhat older than figure 1 ; both figures greatly magni- 

 fied. 



Fig. 3. Youngest stage of Nareda observed ; seen in profile. 



Fig. 4. Somewhat more advanced than figure 3, the pigment spots 

 have increased in number, the tentacles of the head make their appear- 

 ance; seen in profile. 



Fig. 5. Older stage, in which the difference in width between the an- 

 terior disk and the body has attained its maximum, large increase in 

 number of pigment spots, diminution in diameter of digestive cavity ; 

 seen in profile. 



Fig. 6. Posterior extremity of young Nareda, about in the condition 

 of figure 5, showing the intestine and place of formation of new rings, 

 seen in profile. 



