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 7). 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 Stylasteride 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-systems 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 
Stylasteride, 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 veesentlige Punkter afviger fra Anthozoerne hvortil den 
maaske slet ikke engang kan henfqres.” 
