232 HARGITT, [VOL. II. 



to warrant any formal deductions, but taken in connection with 

 others it will not be amiss as showing the facts of variation 

 pertaining to this genus. 



Like Margelis this medusa is quite small when liberated, 

 indeed never attains a size of more than i mm. in diameter, so 

 far as I am aware. In general, it is similar in organization to 

 Margelis, has four radial canals and four primary tentacles, 

 between which a second series of the same number soon arises. 

 Like Margelis there is apparently a fair degree of constancy in 

 meristic features. Three trimerous specimens occurred in the 

 lot, which comprised the extent of variations along this line. 

 There were, however, considerable variations of size, form, etc., 

 which increased the total to at least five per cent. It must 

 not be forgotten, however, that the extreme minuteness of 

 specimens, necessitating the constant use of the microscope, 

 might easily involve an oversight of specimens in sufficient 

 numbers to materially raise this ratio of variation. 



Gonionemus. 



It is among the members of this genus that I have been able 

 to work out the most numerous and detailed series of varia- 

 tions. The total number of specimens of Gonionemus exam- 

 ined during the progress of the work was more than two 

 thousand. (Of the first series studied no record was kept.) 

 While smaller than the number of Eucope, to which reference 

 has been made, the number is yet sufficiently large to insure 

 against an unusual per cent which might be clue to local or 

 other incidental influences. Moreover, the collections were 

 made during three summers, and by several collectors, so that 

 the results obtained may be considered as closely approximat- 

 ing the actual state of variation now under way. It is a pleas- 

 ure to acknowledge in this connection courtesies from Messrs. 

 Coe, Parker, Perkins, Gray, and others for permission to exam- 

 ine collections of these, medusae made by them, which has 

 facilitated my work. 



In these studies attention has been directed chiefly to the 

 following structures : i, radial canals; 2, gonads ; 3, manubrium ; 



