306 On the Young Stages of a few Annelids. 



floating on the surface, so that frequently the examination of a 

 few rods will give us at once what otherwise we should find 

 only after a protracted search. 



Violent storms which throw upon the beaches masses of sea- 

 weed, furnish a rich harvest of small animals, attached to the 

 fronds, or concealed between the roots, only to be found in 

 hiding-places inaccessible at other times. The roots of Lami- 

 naria are the resort of thousands of young Echinoderms, An- 

 nelids, Crustacea, and Mollusks, after they have ceased to 

 swarm near the surface of the water, and have assumed some- 

 what the habits of the adult. Not even the dredge will root 

 these up, and we must snatch at the favorable chances an 

 opportune storm throws in our way. 



I have already shown in my different papers on the Embry- 

 ology of Echinoderms* and Acalephs,f how useful knowledge 

 of this kind proved in order to complete missing links in the 

 history of their development. In the following pages will be 

 given some of the results obtained for a few Annelids by a 

 similar mode of procedure. 



Planaria. 



Before the observations of Miiller;}: on the development of 

 Planarians, the embryos had not been found to differ materially 



* Agassiz, Alexander. On the Embryology of Astracanthion berylinus, 

 Ag ; in Proc. Am. Acad. April 14, 1863. 



Agassiz, Alexander. On the Embryology of Echinoderms ; in Mem. Am. 

 Acad. IX. 1864. 



Agassiz, Alexander. Embryology of the Star-fish ; in Vol. 5 of Agassiz's 

 Cont. Nat. Hist, of U. S. 1865. 



f Agassiz, Alexander. North American Acalephse ; No. 2 of Illustrated Cata- 

 logue of Museum of Comparative Zoology. 1865. 



% Muller, Johannes. Ueber eine eigenthiimliche Wurmlarve aus der Classe 

 der Turbellarien u. aus der Familie der Planarien ; in Archiv f. Anat. u. Phys. 

 1850. p. 485. Plate XII-XIII. 



