34 THE VOYAGE OF H.M.S. CHALLENGER. 



relation to the coral. The true polyp body, he says, lies at the bottom of the central 

 cavity of the calicle. It is very small, almost hemispherical in form, and provided with 

 an apparently protrusible beak or proboscis, which is sharply defined and bluntly conical 

 in form, and on which no mouth opening was observable. From the circumference of 

 the head of the polyp proceed the narrowly cylindrical tentacles which correspond in 

 number to the infoldings of the calicle. Their lower region is inserted in the interseptal 

 canals, while their upper parts project free from the foldings in between the so-called 

 septa, and usually bend with their bluntly rounded ends towards the centre. No distinct 

 connection between the different polyp cavities was to be observed. They all seemed 

 completely closed below ; but it is to be remarked that the whole upper lining part of 

 the coral is highly porous. Often there were to be found outside real polyp cavities in 

 the inner mass of the coral near the surface, small cavities apparently everywhere closed, 

 wherein were included one or several spherical bodies (eggs ?). Portions of the coral 

 were decalcified in acetic acid. The organic basis remaining preserved to a considerable 

 extent the form of the coral, and was composed of a tolerably regular network of apparently 

 fibrous tissue in which were embedded numerous small elliptical nematocysts. The body 

 of the polyp could be prepared out with considerable ease from this mass in connection 

 with its several tentacles, which under the microscope showed themselves beset all over 

 with extremely small tightly -packed nematocysts. 



Although Sars thus suspected the affinity of the Stylasteridse to the Hydroida, his 

 results were insufficient to demonstrate the fact, since he could obtain no satisfactory 

 information concerning the generative structures of the coral which he studied, and he 

 failed entirely to detect the compound nature of the cyclo-sy stems of Allopora, since he 

 regarded the dactylozoids as the tentacles of the gastrozooid, or body of the polyp, 

 as he terms it. He, however, determined a great deal which was of high value. 

 He was the first to make any observations on the structure of the soft parts of the 

 Stylasteridse, and is as yet the only naturalist who has watched a Stylasterid in the 

 living condition. 



He concludes his account with the following words, which show that he was not 

 certain as to the true nature of Allopora, although he considered there were strong 

 grounds for removing it from amongst the Anthozoa : — 



" Af det allerede anforte synes imidlertid med sikkerhed at fremgaa, at viher have for 

 os en Dyreform der i mange vaesentlige Punkter afviger fra Anthozoerne hvortil den 

 niaaske slet ikke engang kan kenftpres." 



