176 THE MEDUSAE. 



of such a proboscis as has been described for some other Aequoridae, nor 

 was the mouth closed in any of the specimens. In the preserved specimens 

 the mouth usually shows the Mesonema condition, with the gastric wall 

 forming merely a narrow fringe around the periphery of the stomach ; 

 though in some specimens this wall is as broad as in life (PI. 36, fig. 9). 

 The contraction is deceptive, for the wall shows no apparent evidences 

 of distortion, and might readily be supposed to be in its normal condition. 

 In comparing the figures of A. macrodactylum and A. maldivensis given by 

 Maas and Browne the only difference in the condition of the mouth is 

 that in A. maldivensis the gastric wall is somewhat broader than in A. macro- 

 dactylum ; and in view of the contractility of this organ, and the fact that 

 both descriptions were taken from preserved specimens, I am convinced 

 that this is due merely to the Maldive being less contracted than the 

 "Siboga" specimens. I may also call attention to the fact that the original 

 and very excellent figures of this species published by Brandt ('38) show the 

 lower gastric wall of considerable breadth, and by no means " rudimentar ; 

 Mund daher fast so gross wie Magendurchmesser " (Maas, : 05, p. 40). 



The small number of canals in the present individuals cannot, in my 

 judgment, be supposed to indicate specific difference from A. macrodactylum, 

 inasmuch as there is no evidence that any of our specimens had reached 

 their maximum development. The presence of gonads does not necessarily 

 indicate a close approach to maturity in this family, for it has been shown 

 that in several species a very considerable number of canals may be added 

 after the sexual organs on the earlier formed canals are of considerable size. 

 Fewkes ('81 b ) indeed has found that in A. groenlandica gonads begin to 

 develop when only a very few canals are formed. The sterile canals 

 described as alternating with fertile canals in various species are to be 

 thus explained; no doubt they would finally develop gonads. They are 

 particularly evident in medium-sized specimens of A. tenuis, and have been 

 figured by Maas (: 05) as well as by Brandt ('38) in A. macrodactylum, while 

 I have myself observed them in several of the present specimens. 



All our specimens were entirely colorless, the gonads and entodermic 

 system opaque and milky. 



Acr/uorea macrodactylum is widely distributed over the Tropical Pacific and 

 the Malaysian region ; it has likewise been recorded from various stations 

 in the Indian Ocean (Maldives, Browne ; Zanzibar, Chun, Goette). 



