STYLASTERIDAE 



21 



Stk 



\ 



only the manubrinm remains as spadix. In his figures (1888 PI. 38 figs. 4 and 6) Hickson has shown 

 cases of such reduced gonophores in Distichopora and the northern Stylaster species also have similar 

 gonophores. Even though such a gonophore structure has not yet been shown in the Bougainmlliidae, 

 yet it is not without a parallel in the athecate 

 Hydroids. In Eudendrium raccmosum (Cavolini) 

 the spadix is bifurcated into two or often three 

 branches, which claw-like embrace the egg-cell 

 (Text fig. E). This is in fact a simplified tropho- 

 disc; an increase in the number of the spadix 

 branchings would very soon lead to the condi- 

 tion we have found in Stylaster roseus and the 

 step from this to the condition in Stylaslcr 

 "i-iinnascens and Stylaster norvegicus is also I II 



short. There is thus no fundamental difference Text-fig. I: Female Gonophore of Endendriumracemostim(Ca.vo\ in i) 



, .... .... . . . r , t_ CM / from the Adriatic (95/i) '). II: semidiagramniatic figure of the 



present, which justifies the raising of the My la- . . . , 



female gonophore of Stylaster roseus. o = ovum, stk = stalk of 



steridae to a special order. the gonophore, sto l= = main stolon of the gonophore, rfo a = secon- 



dary stolon of the gonophore, sp = blind sacs of the spadix. 

 There is one condition however to which 



Hick sou ascribes even greater weight. In his work on the gonophores in Distichopora and Allopora 

 he states (1891 p. 392) : Comparing the adelocodonic gouophores (fig. 4) with the male gouophores of 

 Allopora (fig. 5), two points of difference may be observed. In the first place the endoderm completely 

 surrounds the gonad in the latter, excepting at a small aperture at the distal pole, where it forms the 

 inner wall of a seminal duct. Secondly, there is no layer of ectoderm between this endoderm and the 

 gonad of Distichopora. In the adelocodonic gonophore there are two layers of ectoderm between the 

 gonad and the wall of the gonangium. 



Quite apart from the disagreements between Hickson's results and the present studies on the 

 gonophore structure in the Stylastcridcn\ his argumentation is hardly maintainable in the light of later 

 studies on the gonophores of the Hydroids. In a species such as Coryne fruticosa Kuhn (1910 p. 65, 

 Taf. 6 figs. 2527) has shown, that the gonophores have just the structure which Hickson gives as 

 characteristic of Distichopora and Allopora. It is thus not without a parallel in the Hydroids. Much 

 more rare then is the still simpler gonophore type in the Hydroids, where the endodermal cell-layer 

 has also disappeared; nor is this without a parallel however; according to Kuhn (1912 p. 199) it has 

 been found in Gymnogonos crassicornis and in Eudendrium simplex. 



The only gonophore type in the Stylasteridae, which in reality differs greatly from the known 

 conditions in the Hydroids, is the male gonophore in Pliobothrus symmctricus. With its follicular 

 structure this shows a higher stage in the gouophore structure than any other gonophore we as yet 

 know from the lower Coelenterata. In reality we have here striking evidence of the fact, that the 

 gonophore structure has been greatly overestimated in judging of the phylogeny of the Hydrozoa ; 

 one of the most primitively organised Stylasterids has the most (highly organised gonophore 

 type of all. 



') After specimens from Triest kindly sent me by Hr. Dr. C. Lehnhofer (Innsbruck). 



