REPORT ON THE SIPHONOPIIOR^E. 173 



Family IX. Polypiyidj:, Chun, 1882. 



Polyphyidse, Chun, 86, p. 12. 

 Hippopodidx, Kolliker, 4, p. 28. 



Definition. — Calyconectse polygastricse, with a biserial nectosome, composed of four 

 to six or more opposite nectophores. Cormidia ordinate, separated by equal free inter- 

 nodes, always without bracts. 



The family Polyplryidse differs from the other polygastric Calyconectse in the 

 complete absence of bracts. The nectophores are numerous, and arranged in a biserial 

 nectosome, as in the preceding Desmophyidse, from which they may be derived by the 

 reduction of the bracts. The general composition of the cormidia, as well as the special 

 structure of the single parts composing them, is very similar to that of the other Caly- 

 conectse (mainly Prayidse) ; but in some respects they approach more to the Physonectse. 



The oldest and best known form of Polyphyidse is the common Mediterranean 

 Hippopodius gleba, described and figured so early as 1775, by Forskal, under the name 

 Gleba liippopiis (11, pi. xliii. fig. e). It has been mentioned under very different names 

 by later authors (compare 33, p. 22). The first accurate anatomical description of it was 

 given in 1853 by Kolliker (4), others by Vogt (6) and Leuckart (8). Kolliker observed 

 a second Mediterranean form of this family, which he called Vogtia pentacantha (4, 

 p. 31, Tab. viii.) ; and he established for these two genera the family Hippopodidse, 

 differing from the Physophoridse in the absence of a pneumatophore, from the Diphyidse 

 in the possession of numerous nectophores arranged in a biserial nectosome similar to 

 that of the Agalmidse. Chun afterwards (1882) called the same family Polyphyidse (in 

 opposition to Diphyidse and Monophyidse). Leuckart united the Hippopodidse and 

 Diphyidse in his group Calycophorida? (8). 



Nectosome. — The nectophores of the Polyphyidse are always numerous, at least four 

 to six, often eight to twelve, sometimes more. They are constantly opposed in alternate 

 pairs and arranged in a biserial column, similar to that of the Agalmidse. But a remark- 

 able difference exists in the form and the structure of the trunk. The tubular trunk or 

 common stem of the nectosome, which bears the nectophores, is, in the Agalmidas, 

 Apolemidse, and other Physonectse, the rectilinear prolongation of the trunk of the 

 siphosome, which bears the siphons and gonophores ; the former is the superior and the 

 latter the inferior part of a straight, cylindrical tube. Quite different is the relation of 

 the two parts of the trunk in the Hippo]5odidse, as was first pointed out by Leuckart. 1 

 The superior part of the common stem, or the trunk of the nectosome, is connected with 

 the inferior part, or the trunk of the siphosome, at a small acute angle, which forms 

 the top of the corm. Both descend together from the top, and the deflexed trunk 

 of the nectosome, bent clown upon itself, forms a spiral band which surrounds the 



1 8, p. 303, Taf. xii. fig. 3 ; 35, p. 553, Taf. xlvii. fig. 27. 



