3SO ON A SPECIES OF TUBICOLAR ANNELID 



ferent, in fact, that they were regarded by O. F. Miiller as belonging 

 to a distinct species. 



I sought carefully for evidence of any such " alternation " in 

 Protula Dysteri, but the result was to convince myself that nothing of 

 the kind exists. 



The generative products may indeed almost always be detected, 

 though the ova are very small and indistinct, in the anterior zooid 

 of any still unseparated pair ; and it is therefore clear that the 

 gemmiparous zooid is not asexual, the invariable rule where that 

 separation of the individual into asexual and sexual zooids, which 

 constitutes the so-called " alternation of generations," really exists. 



DESCRIPTION OF FIGURES. 



Pl. I. [XXVI.] 



Vermidom of Prctula Dysteri. 



Single calcareous tube with the worm protruded and expanded. 



An adult Protula extracted from its case, b. branchia, c. testes, d. ova, (dorsal 



view). 

 A Protula undergoing prolification (central view). 

 The produced zooid just set free. 



Junction of parent and derivative zooids (ventral view), a. ciliated canal. 

 Pedal tubercle. 

 Seta and Uncini. 

 Ciliated canal, greatly magnified. 

 Ova — young and completely developed. 

 Spermatozoa — young and completely developed. 



