. The annals and magazine of natural history : zoology, botany, and geology. lyps are quite normal, having twelve tentacles —six inner slightly larger than six outer. In the HawaiianPoeilloj)ore3 the proportion of modified to normal polyps isabout one in twelve, at)d the former are distributed irregularlyover any region of the colony. From an examination ofserial transverse sections there is no question that at theirorigin in the disk the protrusions correspond in position withthe tentacles, only the direction of growth is inwards insteadof outwards. Where three downgrowths occur there are onl
. The annals and magazine of natural history : zoology, botany, and geology. lyps are quite normal, having twelve tentacles —six inner slightly larger than six outer. In the HawaiianPoeilloj)ore3 the proportion of modified to normal polyps isabout one in twelve, at)d the former are distributed irregularlyover any region of the colony. From an examination ofserial transverse sections there is no question that at theirorigin in the disk the protrusions correspond in position withthe tentacles, only the direction of growth is inwards insteadof outwards. Where three downgrowths occur there are onlynine ordinary tentacles, where two downgrowths are presentthere are ten external tentacles, and where one downgrowththere are eleven tentacles ; the missing tentacles are replacedby the modification. Unfortunately the diminution in thenumber of tentacles was not noticed on the living expandedpolyps, indeed such an observation would be very difficultto make considering the smallness of the polyps of Pc>Ci7/o^oraand the closeness of the two circles of tentacles. Transverse section, much enlarged, through an iiitrapolypal tentacle,showing the vacuolated character of the endoderm and the axis ofmesoglcea. The nuclei are few in number, small and irregularlyshaped ; a few symbiotic zooxanthollse are represented. Histologically the downgrowths present certain markedpeculiarities. The relationships to the polypal layers indicatethat the cellular constituents are wholly endodermal, but thecells differ much from those of the ordinary endoderm. Asshown in the various figures they are much longer, whilefig. 5 gives their api)earance when highly magnified. Thecells are much vacuolated, and the various stains employed 472 Prof. J. E. Diiculeii on the indicate very iiieogre protoplasmic contents. The nuclei arefmall, irregular in shape, and comparatively lew in number,and are aggregated towards the margin, where a few zooxan-ihellai also occur similar to others distributed throug
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Keywords: ., bookcentury1800, bookids7annalsmagazi, booksubjectnaturalhistory
