34 THE MEDUSAE. 



viously observed, has been recorded by Agassiz and Mayer ('99, : 02) and by 

 Bigelow (: 04), while two new and easily distinguished species of the genus, 

 JX. pida Agassiz and Mayer (: 02) and N. rubra Vanhoffen (: 02 a ), the first a 

 surface, the second an intermediate form, have been discovered. 



According to Vanhoffen (: 02") five species of Nausithoe are to be distin- 

 guished : — N. punctata Kblliker ('53), JX. clausi Vanhoffen ('92), JX. challenged 

 Haeckel ('80), N. albatrossi Maas ('97), and JX. rubra Vanhoffen (: 02 a ). To 

 these must be added N. pida Agassiz and Mayer (: 02) ; while I agree with 

 Maas (: 03) that the status of N. clavsi is doubtful, my own conclusion on 

 this point being that Vanhbffen's single specimen of JX. clausi was certainly 

 immature and of which JX. picta is probably the adult. 



The status of N. challenged Haeckel ('80), is also doubtful. The only 

 feature distinguishing the two specimens of this species from specimens of 

 JX. punctata of equal size (12 mm. in diameter) seems to be the occurrence in 

 JX. challenged of slight radial furrows at the margin of the central disc. In 

 all other respects the figures represent typical A 7 , punctata of large size and 

 with well-marked pedalia and ring furrow. Vanhoffen (: 02 a ) and Maas (: 03) 

 both consider the sculpture of the central disc a good specific character, but 

 it seems to me, on the contrary, that it is by no means a certain one in the 

 case of alcoholic specimens. This question cannot be settled without an 

 examination of fresh material of N. challenged, but I am of the opinion that 

 the latter name will probably prove to be a synonym either of N. punctata or 

 of N. picta. X. albatrossi Maas seems to be a good species ; it is distinguished 

 from all other species of the genus not only by its very much greater size 

 (40 mm. in diameter), but also by a different arrangement of the gastric cirri, 

 which, as is shown in a figure from life (Maas, '97, pi. 14, fig. 2), are asso- 

 ciated in bundles. N. picta, likewise, is considered by Maas (: 03), who has 

 examined typical specimens, a good species. Although showing no ana- 

 tomical features to separate it from other members of the genus, it seems 

 easily distinguished by its size and by a very characteristic pigmentation 

 of the gonads. There arc, then, probably only four distinct species of 

 Nausithoe, which may be briefly diagnosed as follows: — 



IT. punctata Koiliker ; small ( 12 nun. in diameter), endodermal system color- 

 gonads yellow or brown. Gastric cirri simple Found in all oceans. 



JX. pida \- i - w and Mayer; with large, brilliantly pigmented gonads, 

 red or brown, with very short and broad tentacles; simple gastric cirri; 

 ■i than X. punctata (22 nun. in diameter). 



