LYMNOREA ALEXANDRI. 193 



take a stand opposite to that held by Vanhoffen ('89), maintaining that 

 these organs, as Haeckel ('79) supposed, "are, no doubt, fundamentally radial, 

 but the halves are pushed apart by the channels through which the radiat- 

 ing canals open into the stomach, so that each half joins the half of the 

 adjacent reproductive organ in the interradial plane. There are, in effect, 

 four interradial gonads, although each is to be regarded as the halves of 

 two perradial gonads " (Brooks and Rittenhouse, : 07, p. 435). They have 

 offered no evidence, however, that this is the actual course of development, 

 while their own figures suggest that the gonads are truly interradial, since 

 they are perfectly continuous in the interradii, while entirely discontinuous 

 in the perradii. The fact that the furrows in the interradii along which 

 they suppose the union of the gonads to have taken place are deeper in 

 adults than in the young is further evidence in support of the latter expla- 

 nation. What little evidence is afforded by the present specimens, as well 

 as by a series of Turritopsis nutricula which I have myself examined, is to 

 the same effect, i. e. that the gonads are interradial. 



Lymnorea Mayer, 1900. 



(Non Peron et Lesueur, : 09.) 



Dendroclavinae with but slight development of peduncle ; with numer- 

 ous tentacles ; oral nematocyst knobs numerous, and branched. 



The four species of Lymnorea, as thus limited, L. borealis Mayer (:00 a ), 

 L. ocellata Agassiz and Mayer (: 02), L. norvegica Broch (: 05), and L. alexandri 

 Mayer (: 04), are distinguished from one another only by such minor charac- 

 ters as number of tentacles, length and form of proboscis, and extent of 

 branching of the labial arms, characters all of which change with growth. 

 It is doubtful whether all the species are distinct; but it is impossible to 

 revise them from the published accounts. The description of L. alexandri 

 agrees so well with the specimens in the present collection that I have little 

 hesitation in referring them to that species. 



Lymnorea alexandri Mayer. 



Lymnorea alexandri Mayer, : 04 ; p. 10, pi. 1, figs. l-5 a . 



McCradia species Brooks and Rittenhouse, : 07, p. 435, pi. 31, fig. 8. 



Plate 40, Figs. 3, k; Plate 44, Figs. 11, 12. 

 Acapulco Harbor ; surface ; 4 specimens. 

 The largest specimen measures 2.5 mm. in height by almost 2.5 mm. in 



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