6o HYDROIDA 



The species Eudeiidriuni raiiios^Dii (Pallas), Endciidrimn raiiieuiii (Pallas), and Eiidnidrinii/ race- 

 iiiosniii (Cavolini) are very nearly related to each other, and sterile colonies of the three species are often 

 hardly distinguished with certainty. While in Eiidoidriuiii nuiicniii the male gonophores are borne on 

 polyps fully developed, they are seated, in Eitdciidriuiii raiiiosiiin and Eiidfiidriiiiii raccuiosiiiii round polyps 

 wholly reduced. This conformity of the two last-mentioned species, the homogeneous structure of their 

 colonies, and several other features common to them, which struck me during my inquiry into the Adriatic 

 hydroids (1912), really led me to consider, though with some doubt, Eudciidriiiin rucciiiositiii as a synonyme 

 of Eudciidriniii nunosiuii. This supposition, however, is hardly right. By the liberality of Dr. C. Lehnho- 

 fer at Innsbruck I have afterwards had the opportunity of examining more closely unquestionable colo- 

 nies of Eudeiidrium racemosum from Triest, and of recognizing in these the characteristic criteria distin- 

 guishing this species from Etidendrhim rainosiii/i. Occasionally are found developed in the polyj? of F^ii- 

 dendrmm racoiiosiiin peculiar organs which are not traceable in other species of the genus, and which, like 

 analogous organs in other hydroids, have to be designated as "nematophores" (cp. Weismann 1S82). 

 Elsewhere the presence or the absence of these formations is looked upon as a generic character among 

 the hydroids. But this view is here hardly justifiable, as in Eitdriidn'in/i niconosiiin the nematophores occur 

 quite irregularly and are rather rare; in some colonies they are even entirely wanting, and such colonies, 

 when sterile, or when only male individuals occur, cannot be distinguished with certainty from Eudciidriiiiii 

 ramosum. — The other distinguishing mark between the two species is the spadix of the female gono- 

 phores. While, according to the descriptions in hand, the spadi.x of Eiidcndriiuii rauiositin is unbranched, 

 that of Eudoidruun racciiiosuui is, on the contrary, bifurcate or divided into three branches, embracing 

 the ovum like a claw (s. Broch 1914 Stylasteridae p. 24, Text-fig. I) I regret that I have not succeeded 

 in getting hold of fertile female colonies of Eiidciidriuiii raii/osmn^ so as to be unable to give a draw- 

 ing, from new material, of the female gonophore of this species. 



From the statements above it is clear that Eiideiidriuiii raiiiosiiiii has most probably been 

 several times confused with Eudciidriitvi raceiiiosiiii/. On the other hand, as I have earlier pointed 

 out, a confusion with Eudciidriiiiii raiiicitvi^ particularly from the northern seas has also often taken 

 place, and the geographical data presently in hand as to Eudoidriuiii raii/osniii are, therefore, of most 

 questionable value. A closer inquiry into the colonies from Faxebugt (Iceland) recorded by S rem unds- 

 son (1911) as Eitdciidriiiiu raiuosuiii, shows that we here really face typical Eiidrndriitiu nuiiniiu. 

 However, the single specimen of the species which is in hand, shows us that in warmer layers of 

 the Atlantic it may occur as far to the north as Iceland. Tlie occurrence of the species in the northern 

 Atlantic regions, however, has yet to be more closely accounted for. 



Eudendrium Wright! Hartlaub. 

 1859 Eudrndriinn arhiiscula^ Wright, Observations on British Zoophytes, p. 113, pi. 9, fig. 5 — 6. 

 1905 — Wrigliti^ Hartlaub, Die Hydroiden der magalhaensischen Region, p. 547. 



The strongly and irregularly branched colonies have a fascicled main stem, and attain a height 

 of 60 mm. The small branches are annulated above their rise from the mother branch, but are else- 

 where smooth. The polyps have a large number of tentacles. The tentacles have no particularly 



