AMPHINEMA AUSTRALIS. 199 



dinema from the coast of Europe, which is very closely allied to them, the 

 gonads appear to be permanently limited to the manubrium. 



One other American species, Dissoneina turrida Mayer (: OO*"), must also 

 be referred to Amphinema. This species was placed by Mayer in the 

 leptomedusan genus Dissonema on the supposition that the gonads were not 

 situated on the walls of the manubrium, but lay along the radial canals. 

 An examination of Mayer's original specimens has convinced me that this 

 interpretation is erroneous, and that the gonads in reality belong to the 

 walls of the manubrium, whence, in large specimens, they extend out on to 

 the subumbrella, exactly as Haeckel ('79) describes them in Codonorchis. 



The present collection contains two species of Amphinema, one identical 

 with A. australis Mayer, the other with A. turrida Mayer. The series of the 

 latter is particularly instructive, since it illustrates several successive stages 

 in the growth of the gonads. 



Amphinema australis Mayer. 



Stomotoca australis Mayer, : 00'', p. 32, pi. 1, fig. S ; : 04, p. 9. 



Plate 7, Fig. 5; Plate 38, Figs. 10, 11. 



Acapulco Harbor ; surface ; many specimens. 



The largest specimens measured 3 mm. in height by 2.5 mm. in diameter. 



The specimens agree very closely with Mayer's account, and the general 

 form, with high apical projection, is well shown in his figures. In the photo- 

 graph (PI. 7, fig. 5) this is much less prominent than in life. The presence 

 of ectodermic ocelli at the bases of the rudimentary tentacles is a distinguish- 

 ing feature of this species, and one very constant in all the specimens. The 

 number of rudimentary tentacles is also important, for I have never found 

 more than six, even in large individuals with ripe sexual products, while in 

 A. nigosa, according to Mayer (: 00"), there may be as many as fourteen. 



The gonads, not sliown clearly in Mayer's figures, are interradial (PI. 38, 

 fig. 11), though in large specimens only slightly interrupted in the perradii. 

 They are always smooth, without distinct folds or lobes such as are found in 

 A. turrida, and are restricted chiefly to the basal region of the manubrium. 

 The collection contains both males and females. While in ^S". apicafa the 

 two sexes differ from each other both in color and in form (Mayer : 00"), in 

 S. australis they are indistinguishable externally. 



