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, 

 N. picta Agassiz and Mayer (: 02) and N. rubra Vanhoffen (: 02="), 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 Kolliker ('53), N. clausi Vanhoffen ('92), N. cliallengen 

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

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

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

 this point being that Vanhoffen's single specimen of iV. clausi was certainly 

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



The status of iV. cJmllengeri Haeckel ('80), is also doubtful. The only 

 feature distinguishing the two specimens of this species from specimens of 

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

 N. challengeri of slight radial furrows at the margin of the central disc. In 

 all other respects the figures represent typical N. punctata of large size and 

 with well-marked pedalia and ring furrow. Vanhoffen (: 02^) 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. challengeri, 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. N. 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, hkewise, 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 are, then, probably only four distinct species of 

 Nausithoe, which may be briefly diagnosed as follows: — 



N. punctata Kolliker ; small (12 mm. in diameter), endodermal system color- 

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



N. picta Agassiz and Mayer; with large, brilliantly pigmented gonads, 

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

 larger than N. punctata (22 mm. in diameter). 



