STYLASTERIDAE 21 



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

 cases of such reduced gonophores in Disticliopora and the northern Stylastcr species also have similar 

 gonophores. Even thougii such a gonophore structure has not yet been shown in the Bougainvilliidae^ 

 yet it is not without a parallel in the athecate 



Hydroids. In Eudendriuin racemosuni (Cavolini) \ /i-.J ^^^ 



the spadix is bifurcated into two or often three ^Pc ' 



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 Stylastcr roscus and the 



step from this to the condition in Stylastcr '^--sio 



getmnascens and Stylastcr norvcgiciis is also I H 



short. There is thus no fundamental difference Text-fig. I: Female Gonophore of £W<-Kn'r/;(/«mtv/«n.w(« (Cavolini) 



. 1 • 1 • i-r- .1 • • r i.1 c-j ; from the Adriatic (95/i)i). II: semidiagrauimatic figure of the 



present, which nistifies the raising of the Stvla- , , , / , , *^ f „ , 



^ -^ o . temale gonophore of ittylaster rosi-us. = ovum, stk = stalk of 



steridac to a special order. the gonophore, .sYi1j = main stolon of the gonophore, i<o„=secon- 



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



There is one condition howe\'er to which 



Hickson ascribes even greater weight. In his work on the gonophores in Disticliopora and AUopora 



he states (1891 p. 392): Comparing the adelocodonic gonophores (fig. 4) with the male gonophores 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. Secondh-, there is no layer of ectoderm between this endoderm and the 



gonad of Disticliopora. In the adelocodonic gonophore there are two la\'ers of ectoderm between the 



gonad and the wall of the gonangium . 



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

 gonophore structure in the Stylastcridac, his argumentation is hardly maintainable in the light of later 

 studies on the gonophores of the Hydroids. In a species such as Corync frnticosa Kiihn (1910 p. 65, 

 Taf. 6 figs. 25— 27) has .shown, that the gonophores have just the structure which Hickson gives as 

 characteristic of Disticliopora 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 eiidodermal cell-layer 

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

 been found in Gymnogonos crassiconiis and in Eudendrium simplex. 



The only gonophore type in the Stylastcridac, which in realit>' differs greatly from the known 

 conditions in the Hydroids, is the male gonophore in Pliobotlirus syminctriciis. With its follicular 

 structure this shows a higher stage in the gonophore structure than any other gonophore w-e 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 St\lasterids has the most |highly organised gonophore 

 type of all. 



'J After specimens from Triest kindlj- sent me by Hr. Dr. C. Lehnliofer (Innsbruck). 



