356 



BULLETIN OF THE BUREAU OF FISHERIES 



The dimensions of the specimens of Aglantha from the Gulf of Maine, compared 

 with their states of sexual maturity, corroborate all previous studies of the genus to 

 the effect that there is a wide range of variation with respect to the size attained by 

 this medusa at maturity. At the one extreme is a large race in which the gonads do 

 not reach full size until the bell is 20 millimeters high or even higher, and there seems 

 to be every gradation from this down to specimens in which the sex organs are already 

 well developed and the eggs plainly visible when the bell is only 6 to 10 millimeters 

 high. The Aglanthas from Massachusetts Bay, described by Alexander Agassiz 

 (1865) as upwards of 25 millimeters high when adult and with the gonads just 

 appearing in specimens of 5 to 8 millimeters, were among the largest known repre- 

 sentatives of the species. Most of the Aglanthas collected by the Albatross from 

 February to May, 1920, were likewise large, as appears from the following table: 



A large variety was also represented among the Aglanthas taken in May, 1915, 

 and part (just what proportion is yet to be determined) of the swarm of young just 

 mentioned as encountered off Gloucester on October 31, 1916, were also destined to 

 grow large, for the series taken included many specimens up to 10 millimeters high 

 but without visible trace of gonads. But that same swarm yielded many Aglanthas 

 with gonads of good size and (in the case of the females) eggs already visible, although 

 the bells were only 6 to 7 millimeters high. Our largest catches of the "small" 

 Aglantha were in Massachusetts Bay and especially at Provincetown on July 19 and 

 20, 1916 (stations 10340 to 10343), when specimens sexually mature, though only 

 6 to 10 millimeters high, were abundant and no large ones were taken. Examples of 

 this small variety have also been recorded by Hargitt 95 (1902 and 1905) from off 

 Chatham, August 19, 1902. 



These data suggest that the large race usually predominates in the gulf during 

 the cold season, giving place to smaller specimens during the warm; and the occur- 

 rence of large and small specimens side by side in Massachusetts Bay in October, 

 which I have just mentioned, may mark the transition from the season when most 

 of the Aglanthas are small to that during which they average large. The presence of 

 occasional large specimens in midsummer — for instance, off Grand Manan on August 

 13, 1913, and in Massachusetts Bay in summer and autumn — shows that there is no 

 hard and fast rule. 



To settle the true relationship of the two races to each other, to the physical 

 state of the water, and to their origin in the gulf, whether local or immigrant, calls for 

 a study more intensive than has yet been devoted to the genus. For the present the 



•• Described by him as a new species, "A. conica." 



