OCTOCANNA POLYISTEMA. 169 



Browne (: OS*") entirely disprove the view advanced by Clans ('80) that 

 Octocanna is merely the young of Aequorea; and on account of the form 

 of the stomach and the determinate number of radial canals there is good 

 reason to believe that this genus is more closely related to the typical 

 Eucopidae than it is to the Aequoridae, with which it was classed by 

 Haeckel. The large number of canals, however, together with the presence 

 of excretory papillae and pores at the bases of the tentacles, suggest that 

 Maas (: 05, p. 38) is correct in calling it an " Ubergangsgruppe " between 

 the two families. The discovery by Browne (: 05"') of small specimens of 

 0. -polynema with only eight tentacles, though with developed gonads, shows 

 conclusively that Maas (: 05) was correct in suggesting that 0. oetonema 

 Haeckel with eight tentacles was nothing more than the young of 0. iiolynema 

 Haeckel with sixteen or more tentacles. Since both the " Siboga " speci- 

 mens and those recorded from Ceylon by Browne (: 05'') are referable to 

 O. polynema, this species now stands alone in the genus. In the present col- 

 lection there are two specimens of Octocanna of which the specific identity 

 is hard to determine. In several important features, especially in the 

 form of the bell, and in the having only eight tentacles, they differ from 

 adult 0. poli/nema; but on account of the small number of specimens it is 

 possible that the final number of tentacles is not yet attained in spite of 

 the fact that the gonads contain large ova. For this reason it seems best to 

 class them provisionally as O. folynema, at least until their affinities can be 

 more definitely determined from the study of a larger series. 



Octocanna polynema Haeckel. 



Octocanna polynema H^ckel, '79 p. 214; Maas, : 05, p. 38; Browne, -.05'', p. 144, pi. 2, 



figs. 8-10. 

 Octocanna oetonema Haeckel, '79, p. 21.3. 



Plate 6, figs. 6, 10; Plate 38, figs. i-i. 



Acapulco Harbor; surface; 2 specimens, 10 mm. high by 8 mm. in 

 diameter. 



In both specimens the gelatinous substance is so thick that the bell is 

 higher than broad, while the bell cavity is extremely shallow (PI. 6, 

 fig. 10). In most of the specimens of 0. jiolynema which have previously 

 been recorded the bell was rather low ; but Browne (: 05^ p. 144) found a 

 single specimen in which the umbrella was very thick and the cavity of 

 the bell shallow. Apparently, then, the form of the bell, striking though 



