118 THE MEDUSAE. 



tains that all described forms of Aglaura in reality belong to but one 

 species, A. hemistoma. According to Maas (: 05, : 06°), however, A. pris- 

 matica, described by him ('97) from the Gulf of Panama, and since recorded 

 by Agassiz and Mayer ('99, : 02) from the Fiji Islands and Tropical Pacific, 

 as well as by himself from the collections of the " Siboga " and from Am- 

 boina, is so well characterized by prismatic, octagonal outline, small size 

 (3-4 mm. high by about 3 mm. broad) and early appearance of the gonads, 

 as to be worthy of recognition. Since the octagonal outline is considered 

 by Maas (: 05, p. 58) the most distinctive character of A. prismatica I studied 

 living material with especial care and found that the outline is variable ; for 

 though most of the specimens were nearly circular in cross section, a few 

 were distinctly prismatic ; and these conditions are retained after preser- 

 vation. Because of this variation I believe that this character is no more 

 important than the general outline of the bell, which is well known to 

 be subject to great diversity in this genus in different states of muscular 

 contraction. 



I have been able likewise to test the supposed difference in time of 

 appearance of the gonads on specimens both from the Atlantic and from 

 the Pacific. According to Maas (: 05) the Atlantic (Mediterranean) species 

 shows no gonads until about 3 ram. high ; but I have observed gonads 

 (spherical) in a specimen from the West Indies not more than 1.5 mm. 

 high ; while in several specimens 2.5-3 mm. high they were already large 

 and sausage-shaped. This character, then, is no doubt variable, as Maas 

 suggests (:05, p. 59) and cannot be considered as separating an Atlantic 

 from a Pacific form. 



Since I am unable to find any constant characters distinguishing the 

 present specimens from others from the West Indies, I refer them to 

 A. hemistoma ; and inasmuch as many of the specimens were taken near 

 the type locality of A. prismatica, I see no reason to retain the latter 

 longer as a distinct species, or even variety. In all probability the present 

 series is specifically identical also with the specimens recorded by Agassiz 

 and Mayer (: 02, p. 150) as A. prismatica, and stated by them to be generally 

 distributed over the tropical regions of the Pacific ; but which, according 

 to their earlier figure ('99, PI. 4, fig. 13), are circular, not prismatic, in 

 outline. Comparison shows that the specimens recorded by me (: 04) from 

 the Maldives as A. prismatica are also identical with the present series. 



