OP MEDUS/E MADE BY WILLIAM KEITH BHOUKS. 23 



was found by Brooks at Beaufort, North Carolina, and is figured in plate 6^.A. It makes its 

 appearance upon the surface along the coast of New England in August when large medusae 

 are found. The young rarely come to view, but remain in deep water. 



Varieties and development. The egg develops into a free-swimming planula which 

 soon attaches itself to the bottom and develops into a scyphostoma having normally 4 ten- 

 tacles. R. P. Bigelow, 1880, states that the so-called "Chrysaora" of the Chesapeake, which 

 is only a brackish-water, abortive variety of Dactylometra, develops from an ephyra through a 

 Pelagia stage, wherein it has only 8 tentacles and 16 lappets, and Brooks has figured the ephyrae 

 in the text figures here shown. 



The present writer found considerable numbers of Chrysaora-like medusae in Hampton 

 Roads and Norfolk Harbor, Virginia, and in St. Mary's River, Maryland, early in Novem- 

 ber, 1904 and 1905. These were generally pale milky-yellow in color and lacked the rich 

 brown pigment and the 16 pigmented, radial areas seen upon the exumbrella of Dactylome tra 

 quinquecirrha. Others had a red-brown spot at the apex of the exumbrella, and surrounding 

 this was a star-like zone of red-brown streaks with pointed ends directed outward. The 

 axial ribs of the mouth-arms (palps) were red-brown. Although all were in the Chrysaora 

 condition and had only 3 tentacles and 4 lappets in each octant, some appeared to be fully 

 mature or with gonads nearly ripe. The exumbrella surface and the palps were covered 

 with dull milky-yellow clusters of nematocysts. There were 8 marginal sense-organs as in 

 Dact\lometra, but only 24 tentacles and 32 marginal lappets. None of the medusas were, 

 however, as large as is commonly seen in full-grown Dactylometra quinquecirrha, the largest 

 Chrysaora-like medusa seen in Norfolk harbor being only 105 mm. in diameter. It should 

 be borne in mind that D. quinquecirrha does not usually attain 48 marginal lappets and 40 

 tentacles until the medusa is 120 mm. in diameter, and it seems therefore that the so-called 

 Chrysaora of the Chesapeake is only a stunted Dactylometra which becomes mature in the 

 Chrysaora stage, and its pale coloration may be a local peculiarity due to unfavorable con- 

 ditions of confinement in brackish water. In the purer ocean water at (he mouth of Chesapeake 

 Bay the medusns develop into the Dact\lometra condition with 40 tentacles. These conditions 

 are also found in Narragansett Bay, Rhode Island, where in relatively pure clean water the 

 medusae have 40 tentacles, but in brackish estuaries they often become mature with only 24 

 tentacles and are pale in color. 



