HYDRO! DA ._ 



transverse belts. This peculiarity we find slightly indicated even in some Bovgainvilliidac. But onlv 

 in the Endendriidac it has become a character plainly distinctive. Further, the endoderm in the well 

 defined hypostome shows the same structure as in the thecaphore liydroids, and is more strongly differ- 

 entiated than in the BougaiiiTilliid(u\ the indifferent cells having gained the ascendency, and the number 

 of the mucous gland cells having been reduced to a mininnun. Whether these peculiarities are indic- 

 ative of a nearer relationship between the Endnidn'/dac and the thecaphore hydroids, is a question 

 which it would here be out of place to enlarge ui3on. 



The Eudcndriidac, with their frequently dimorphic development of the stinging cells, also pre- 

 sent a parallel to the Sfylasfrridac. Besides the small rodformed stinging cells characteristic of all 

 Fili/cra, we also find in several species larger narrowly oval ones, bearing a strong resemblance to 

 those of the Stylasteridac. The latter are large, but of the same shape as the small stinging cells of 

 J\/yn'of/ifla. We probably here face a phenomenon of con\ergency, the reason of which, however, at 

 the present stage of our knowledge of the biology of the Coclenterata, \\ e cannot account for with 

 any certainty. Wherever the larger stinging cells occur in the Endendriidac they are accumulated in 

 particular stinging organs. 



Eudendrium Ehrenberg. 



Upright colonies with branched liydrocaulus. The jDolyps are broad and distincth' set off from 

 the stem, which is covered with a vigorous chitinous perisarc. The JJohp has a single whorl of fili- 

 form tentacles. Above the tentacle whorl the polyp is suddenly tapering and ends into a capitate or 

 trumpetshaped proboscis, which is seated, with a narrow base, above the tentacle whorl. The gono- 

 phores are developed on normal or reduced polyps, or placed singly on the branches. 



Kiihn (1913, p. 48) states that the polyp tentacles of Eudnidriii/ii "nach einander vorsprossen 

 und dadurch sich als Angehorige verschiedener Wirtel zu erkennen geben". Later on (1. c. p. 247) he 

 again mentions this peculiarity as a refutatory argument against the adoption of a nearer relationship 

 to the thecaphore hydroids; in the passage last quoted he apparently bases his opinion essentially on All- 

 man (1872). A closer inquiry, on new material, gave no hold to the statement of Allman and Kiih n that 

 the tentacles should appear successi\ely. In the numerous colonies examined of FAidcndriiun ratncum 

 (Pallas) and Eiide?idriuin Wrighti Hartlaub it could be ascertained that all the tentacles appear 

 simultaneously. This suggests that the observations of Allman may rather depend on accidental cir- 

 cumstances, and that no special importance must be attached to them as reminiscences of manyrowed 

 tentacle-whorls of the ancestors or as proofs of a nearer or remoter relationship to the Bo2igatnvil- 

 liidac or to the thecaphore hydroids. 



Eudendrium rameum (Pallas) Thompson. 



1766 Tubularia raiiiea^ Pallas, Elenchus zoophytorum, p. 83. 



1844 Eudendrium rameum^ Thompson, Report on the Fauna of Ireland, p. 283. 



1887 — ramosum, Bergh, Karahavets goplepol'yper, p. 332. 



The Ingolf-Expedition. V. 6. 



