CALYCOPHORAE. ' 179 



of Ainphicaryon is a bract. Indeed the actual course of development in that 

 genus seems quite opposed to such a conclusion (p. 195). The other arguments 

 adduced in favor of a double origin of the nectophores of the Prayids seem of 

 no more weight. 



Chun ('98a) has so thoroughly discussed this question, that it is unnecessary 

 to do more here than state my agreement with his general conclusion that the 

 two bells of Diphyids and others are homologous — both are pure nectophores. 

 The very significant fact remains however, that in Diphyids and Abylids the 

 anterior and posterior bells are structurally dissimilar, while in Prayids, Stephan- 

 ophyids, and Hippopodids the two or more bells are all structurally alike. 



Chun ('97b, p. 13) maintains that the "Diphyes ornata" of Kefferstein 

 and Ehlers ('61) is a connecting link between these two types. But no one 

 since Kefferstein and Ehlers has ever seen a Siphonophore answering to their 

 description of this species, and apart from this doubtful form, the distinction 

 between the posterior bells of Diphyids and Abylids on the one hand, and those 

 of Prayids and Hippopodids on the other is perfectly clear cut. It therefore 

 seems more important as a systematic character than Chun ('97b) supposed. 



On the other hand the number of nectophores, as most students now agree, 

 whether two or more, is of comparatively little importance, because while the 

 Hippopodiidae, with several, are undoubtedly a natural group, Prayids and 

 some Diphyids normally develop a succession of bells, though they successively 

 cast off the older ones. This is especially true of Praya cymbiformis (Chun, 

 '97a, p. 66, fig. 8), and of Galeolaria. Since therefore, there is no question 

 but that the bells of Prayids and of Hippopodids are budded in the same 

 fundamental manner (Chun, '97a, p. 66), the only essential difference, so far as 

 their number is concerned, is that they are retained longer in one group than 

 in the other. This fact, together with the structural unity of all the bells in the 

 Hippopodids as well as in the Prayids points to a closer relationship between 

 the two, than between either of them and the Diphyids or Abylids. The 

 absence of bracts in Hippopodids demarks them so definitely from their allies, 

 that it undoubtedly justifies the distinct family recognized by Chun. 



We have now to consider the most puzzling Calycophorids of all, namely 

 the forms usually grouped together as Monophyidae (Haeckel, '88b, Chun, '97b, 

 Lens and Van Riemsdijk, :08). These animals agree in that neither second 

 nectophores nor "reserve buds" are ever formed, and that, so far as known, 

 their groups of appendages are detached to become free-swimming Eudoxids; 

 but they differ widely from one another in form, and although as a rule external 



