364 BULLETIN OF THE BUREAU OF FISHERIES 



After fertilization the developing eggs remain in small pouches along the free 

 margins of the mouth arms, where, by total and unequal segmentation, they form 

 first a blastula, then a gastrula, and finally a ciliated pear-shaped planula. These 

 planuhe, which swim actively, are shaken loose from the mouth arms of the parent, 

 often accidentally by the stranding of the latter on the beach, and settle to bottom, 

 where they become attached by the wide (anterior) end, to develop into the "scy- 

 phostoma," which finally grows to a height of about 4 millimeters with 24 tentacles. 

 The " scyphostoma " then produces as many as 12 disklike "ephyrae," as the young 

 medusae are called, cutting them off by a series of annular constrictions. 



In the northern part of its range one generation of Aurelia is produced each 

 year, the winter being passed in the scyphostoma stage, and the young medusae 

 appearing later and later in the season from south to north, corresponding to the 

 difference in temperature of the water with the latitude. Thus Bumpus (1898 and 

 1898a), Hargitt (1905 and 1905a), and Fish (1925) have found both the ephyrae and 

 the slightly older medusae near Woods Hole from March to May. Many have grown 

 to a diameter of 1 to 2 inches there by April (Mead, 1898) and to 4 to 5 inches by 

 mid May, 6 but few if any Aurelia appear in Massachusetts Bay before May (we found 

 none there during that month in 1915 or in 1920), and it is not until July that they 

 attain their full size of 6 to 10 inches north of Cape Cod. 



According to Louis Agassiz (1862, p. 76), the Aurelia off Massachusetts become 

 sexually mature late in July and through August, which I can corroborate, having 

 found the mouth arms of all large adults examined at that season laden with develop- 

 ing eggs and planuhe. No doubt they continue producing young from that time 

 onward, through September and October, until they are destroyed by the autumn 

 gales, which seems to be their normal fate. According to Mayer (1910), Aurelia 

 does not mature until September in the Eastport region, but I have never seen 

 nor heard of one in the Gulf of Maine after October. 



It is probable that the breeding season of Aurelia and the seasonal succession of 

 its generations are not so definite in the warmer parts of its range, for I have seen 

 large specimens in April in Santiago Bay, Cuba (according to Mayer (1910) Aurelia 

 matures in May at the Tortugas, Fla.), others collected in Barataria Bay, La., 

 during the last week in September, and half-grown individuals taken in the Indian 

 River, Fla., as late as the second week of December. 



Other Scypliomedusse 



Only one other scyphomedusa (Phacellophora ornata) has yet been reported from 

 the inner parts of the Gulf of Maine, and it has been reported so seldom that nothing 

 can yet be said of its distribution, either seasonal or geographic, except that it must 

 be very rare there because it grows to so large a size (up to IS inches in diameter) 

 that it would be a very conspicuous object if abundant. It has a very wide dis- 

 tribution in latitude, for Browne (1908) has reported a Phacellophora, indistin- 

 guishable from the Gulf of Maine species, from the South Atlantic off Montevideo. 

 The recorded captures in the gulf are Eastport, three specimens, 1868 (Verrill, 1869); 



« An occasional ephyra of Aurelia has been found at Woods Hole as late in the season as mid June. Fish (1925) has also re- 

 ported its ephyrse there in late summer and early autumn, but it is doubtful whether this second brood survives the winter. 



