PEGANTHA LAEVIS. 



97 



The gelatinous substance of the disc, always thin, first appears at about 

 the stage represented in PI. 26, fig. 4. As already noted (p. 92), no canal 

 system is developed. The velum first appears as a ridge-like ectodermic 

 thickening just oral to the nerve ring (PI. 24, fig. 8). With further develop- 

 ment it increases in breadth until it attains the practically adult condition 

 represented in cross section (PI. 24, fig. 7). 



The medusa is now ready for independent existence, and swims vigorously, 

 as I observed in living specimens. Metschnikoff ('86") has found a similar 

 active condition in Cunina proboscidea. But Stchelkanowzew, writing of the 

 same species, declares (: 06, p. 478) that the young are mere sacs full of gen- 

 ital products, never fitted for independent existence. Both these authors 

 agree that in Cunina the parasitic generation becomes sexually mature at 

 a stage no more advanced than that above described (PL 26, fig. 5). 

 This is not the case in Pegantha, although the fact that at this stage the 

 ectoderm of the oral gastric wall is already many cells deep (PI. 24, fig. 7) 

 very strongly suggests that the medusae are nearly mature and that the 

 sexual products would soon be developed. The important systematic feat- 

 ure of the oldest medusae, i. e. lack of canals and of otoporpae, has 

 already been noted (p. 92) in the systematic account of this species. 



Pegantha laevis, sp. nov. 

 Plate 16, Fig. 1 ; Plate 20, Figs, h-6 ; Plate 27, Figs. 1-7. 



I likewise found an example of this species in the collection made by 

 the " Albatross " in the Hawaiian Islands. 



The bell is very flat for this genus, being only about one fourth as high 

 as broad; the disc lenticular; the exumbrellar surface of the disc smooth, 

 without any trace of sculpture (PI. 16, fig. /) ; but, as in all other members 

 of the genus, there are slight ridges on tin; marginal lappets along the lines 

 of the otoporpae. There is also a slight coronal furrow, separating the 

 central disc from the marginal zone. The gelatinuous substance is softer 



