ON rARAWJlIGHTIA ROBUSTA. 193 



The developing- liydranth sliows a very marked resem- 

 blance to tlie adult structure of an undescribed Eudendriuni- 

 like species, which was dredged off Bird Island last year by 

 the museum collector. 



In the annexed illustration are shown, side by side, vertical 

 sections of the adult polyp of the Eudendrium (a) and of the 

 developing polyp of Parawrightia (b). 



The striking' similarity in structure in the two cases is 

 remarkable. At this stage in the development there is no 

 hypostome, and the elongated endoderm is spread out in a 

 fan-shaped manner so as to be widely exposed to the exterior. 

 The reflexed ectoderm (r. e.), the arrangement of the endo- 

 derm over it (/. en.), and the origin of the tentacles (t.) may 

 be directly compared with the condition seen in the adult 

 })olyp of the supposed Eudendrium. 'J'he central portion of 

 endoderm (c. en.), consisting of very elongated cells, is 

 essentially alike in the two cases. The digestive cavities 

 {d. g.) are both exceptionally narrow. In the Eudendrium 

 the perisarc is less strongly developed ; but it does extend 

 over the base of the polyp (^j.) to form a kind of calyx, as in 

 Parawrightia. 



It is, of course, debatable how far such a resemblance is to 

 be regarded as arising through genetic relationships ; but the 

 similarity of structure in the two cases is so close that the 

 matter appeared worthy of record ; and it is not unreasonable 

 to assume the possibility that the mode of development of the 

 hydranth may give some hints of phylogenetic significance. 



(4) Gonosome. — The sexes are separate, male and female 

 gonophores being formed on different colonies. The gono- 

 phores, whether male or female, arise on the stems carrying 

 the hydranths. As a rule only one gonophore is produced on 

 a stem, and it is generally situated not far fi'om the polyp. 

 The gonophore, like a lateral polyp, arises by proliferation of 

 a patch of ectoderm and endoderm, which grows through the 

 perisarc in the form of a swelling, and is at first only covered 

 by a very thin membrane. 



Ultimately the gonophore becomes surrounded by a uni- 



