60 HYDROIDA 



The species Eudendrium ramosum (Pallas), Eudendrium rameum (Pallas), and Eudendrium race- 

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

 hardly distinguished with certainty. While in Eudendrium rameum the male gonophores are borne on 

 polyps fully developed, they are seated, in Eudendrium ramosum and Eudendrium raccmosum 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, Eudendrium racemosum as a synonyme 

 of Eudendrium ramosum. This supposition, however, is hardly right. By the liberality of Dr. C. L e h n h o- 

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

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

 guishing this species from Eudendrium ramosum. Occasionally are found developed in the polyp of Eu- 

 dendrium racemosum 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 1882). 

 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 Eudendrium racemostim 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 Eudendrium 

 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 spadix of Eudendrium ramosum is unbranched, 

 that of Eudendrium racemosum 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 Eudendrium ramosum, 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 Eudendrium ramosum has most probably been 

 several times confused with Eudendrium racemosum. On the other hand, as I have earlier pointed 

 out, a confusion with Eudendrium rameum, particularly from the northern seas has also often taken 

 place, and the geographical data presently in hand as to Eudendrium ramosum are, therefore, of most 

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

 son (1911) as Eudendrium ramosum, shows that we here really face typical Eudendrium rameum. 

 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. The occurrence of the species in the northern 

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



Eudendrium Wrighti Hartlaub. 



1859 Eudendrium arbuscttla, Wright, Observations on British Zoophytes, p. 113, pi. 9, fig. 5 6. 

 1905 Wrighti, 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 



