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: 
Station 
Height 
of bell in 
milli- 
meters 
State of sexual development 
Station 
Height 
of bell in 
milli- 
meters 
State of sexual development 
20067 
9 
No gonads. 
Do. 
20096 - 
18 
Gonads 6 to 7 millimeters long. 
Gonads 4 millimeters long. 
Gonads 5 millimeters long. 
Gonads 7 to 8 millimeters long. 
Gonads mature, up to 6 to 7 millimeters 
long. 
20129. - 
10 
20129 
18 
20129 
12 
Small gonads. 
Do. 
20069 
21 
20129- 
13 
20088 
23 
20081 
19 
Gonads 2 to 3 millimeters long. 
20116 
26 
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 
n Described by him as a new species, “A. conica.' 
