336 On the Young Stages of a few Annelids. 



reduced to a small circular patch. The changes henceforth 

 are limited to the head, to the increase of the broad flappers 

 and anal cirri, and to the different degrees of development of 

 the antennae, placed, in the stage of Fig. 52, directly one behind 

 the other, although at the outset they originate one beneath 

 the other; there is no trace to be seen of the rings correspond- 

 ing to these antennas, as we should expect theoretically. They 

 lose little by little the ring of vibratile cilia, the head elon- 

 gates, the eyes are brought nearer the base of the antennas, 

 until finally the anterior part of the little Phyllodoce has the 

 shape of Fig. 53, and the broad flappers resemble Fig. 54, 

 while the anal cirri have nearly assumed the shape of 

 Fig. 55. 



From the earliest stages the larva is never very transparent ; 

 it is distinctly tinged with brown, becoming darker with advan- 

 cing age, till in the stage of Fig. 52, marked spots, darker than 

 the main color, appear on the median line, which gives these 

 3 7 oung Annelids such an unmistakable resemblance to an adult 

 Phyllodoce well known to me, and which I had always identi- 

 fied as Phyllodoce maculata Oerst., that I scarcely needed 

 the additional proof of raising these young to the lull grown 

 Phyllodoce to convince myself of their identity. 



On the Types of Development in Annelids. 



Several attempts have been made to classify the larvse of An- 

 nelids. Bnsch,* Muller,f Schultze^: and Claparede,§ have en- 

 deavored to reduce the forms observed to a few general types. 



* Buscn W. Beobachtungen, p. 55. 



f Ml'ller J. Ueber die Jugendzustande einiger Seethiere; in Monatsb. d. 

 Akad der Wise, zu Berlin, 1851, p. 422. 



% Shultze Max. Ueber die Entwickelung von Arenicola piscatorum, nebst 

 Bemerkungen ueber die Entwiekelung anderer Kiemenwurmer; in Abhand. 

 Nat. Ges. zu Halle, iii. 1855. p. 218. 



§ Claparede A. R. E. Beobaehtungen. p. 84. 



