594 GEORGE T. HARGITT 



to the stomach, but hang down freely into the bell in a sausage- 

 like form, being fastened by only one end. Mayer ('07) says 

 that "only female specimens have been observed;" probably 

 this is merely a mistake in Mayer's description; both sexes are 

 known, and the material collected for this study contained males 

 and females in abundance. The medusae occur early in the 

 spring, as a rule, the ones used for this study having been taken 

 early in April at Woods Hole. For the systematic position of 

 these medusae and for a fuller description of their structure 

 reference should be made to systematic papers such as: A. 

 Agassiz ('65), C. W. Hargitt ('04), Mayer ('07). 



Each gonad of Aglantha contains a cavity which is in direct 

 communication with the cavity of the adjacent radial canal; 

 it is by this means that food is supplied to the gonads for the 

 nourishment of the germ cells. In the ovaries there may be an 

 absorption of the smaller oocytes by the growing eggs, but this 

 is not marked nor abundant, nourishment comes chiefly from 

 the food in the canals. The number of cells present in each 

 ovary is very large, and as growth does not begin at the same 

 time in all, a single ovary may show a great many stages in the 

 oogenesis. Consequently the eggs mature at different times and 

 are liberated from the ovary a few at a time. The eggs escape 

 by rupturing the outer ectodermal covering of the gonad, though 

 a few have been found in the cavity of the ovary from which 

 they doubtless escape by a later rupture of the entire wall of 

 the ovary. 



Since the eggs mature at different times the breeding season 

 extends over a longer period than in those Hydrozoa in which 

 all eggs mature at one time; still the breeding season is limited 

 to a few weeks or less. The entire process of growth and matura- 

 tion is carried on and completed within the gonad, and the eggs 

 have formed both polar bodies and are ready for fertilization as 

 soon as they are liberated from the ovary. This is a fortunate 

 circumstance for the study of the oogenesis; since the complete 

 history of the changes passed through in the maturation process 

 may be determined from a study of the gonads of the medusae, 

 it is not necessary to collect liberated eggs. It is in these liber- 



