761 J. IT. ASH WORTH. 



have never beeu recorded iu any Neapolitan specimen of this 

 species. 



With this example iu mind it is not difficult to believe that, 

 iu a species probably widely ranging over the enormous 

 coast-line of the South Atlantic and Pacific Oceans^ some 

 sjieciniens may have become modified in the direction above 

 indicated, so that finally a condition was reached in which 

 some members of the species possess nineteen and others 

 twenty segments. If we suppose that an additional para- 

 podium and gill have been produced, the only alteration 

 necessary to bi-ing such a form into line with A. assimilis 

 would be the loss of a gill at the anterior end of the series. 

 The reduction and absence of the first gill are so frequently 

 observed in A. marina (and to a less extent in almost all 

 other species) that the reduction and eventual loss of the first 

 gill of the hypothetical form are quite conceivable. 



In my opinion the possession of an extra chaotigerous seg- 

 ment, though striking, is scarcely a sufficiently important 

 character to form by itself a test of specific value, and to be 

 used as the sole means of distinguishing two otherwise 

 identical forms. It seems preferable to regard the New 

 Zealand specimens as forming a variety of the species A. 

 assimilis, to which the name af finis may be given indicat- 

 ing its close connection with and resemblance to the type. 



V. Post -larval Stages of Arenicola from the Falk- 

 land Islands. 



After finding multi})le oesophngeal pouches in adult speci- 

 mens of Arenicola assimilis, it occurred to me that I 

 might be iu error in the determination of the species of 

 certain ])ost-larval Areniccdidie from the Falkland Islands, 

 and a re-examination of them became necessary. The 

 specimens were preserved iu, and handed to me in, formalin, 

 and I examined them in that lluid two years ago. On finding 

 nudtii)le cjesophageal glands I had little hesitation in refer- 

 ring them to the species A. claparedii, because at that 



