PHOTOTYPE PLATES NOS. XXL AND XXIL 33 



on the near approach of any hostile object. The fish represented in this association is one of the 

 Pomacentridae, Amphiprion percnla, and the crustacean a prawn, apparently referable to the genus 

 Palsemon. It is remarkable that these commensal representatives of two distinct zoological 

 classes are similarly tinted, although in the case of the prawn the white ground colour is so trans- 

 parent that its red and yellow spots only are visible as the animal swims. The two organisms, 

 it is perhaps desirable to explain, are not found inhabiting the same individual anemone. This 

 highly interesting subject of commensalism receives fuller attention in the chapter that deals 

 specially with coral organisms. 



A feature worthy of note in association with the photographic illustration of this fine 

 anemone, given in Plate XXL, is the presence in various areas of the disk, but notably immediately 

 below the central mouth, of small, white, thread-like patches. These at first sight are liable to be 

 mistaken by zoophytologists for the protruded "acontia," or thread-cells, so highly characteristic 

 of many species of British sea-anemones. As a matter of fact, they are " craspeda " only — 

 structures of an analogous nature that similarly enclose innumerable stinging cells, " cnidae,' 

 but that are not capable of independent protrusion and retraction through special openings 

 "cinclides," in the body wall. In their normal condition these craspeda form, as it were, binding 

 cords to the free edges of the mesenteric tissues, and it is only through forcible rupture, or 

 erosion of the integument, that they make their appearance, as here shown, on the surface of the 

 disk. Another point of interest noticeable in this illustration is the presence of distinct eminences 

 along the outer or distal border of the reflected inferior or aboral surface of the disk. These 

 prominences are of a wart-like aspect, and resemble the tentacula of the superior surface in a state 

 of extreme retraction. They possess a more or less adhesive function, and their presence in this 

 form demands recognition as constituting an essential diagnostic feature. 



It not having been found possible to identify the species now under consideration with any 

 previously-described kind, the author has bestowed upon it the title of Discosoma Haddoni. 

 The specific name is given by way of compliment to Prof. A. C. Haddon, of the Royal College 

 of Science, Dublin, who has added much to our knowledge of the anatomy of the Anthozoa 

 generally, in addition to having collected many of the species illustrated in this volume during 

 his recent explorations in Torres Strait. 



PLATE XXII. 



STINGING ANEMONES, ICTINODENDRON AND MEGILSCTIS. 



The anemones illustrated in this photographic reproduction present a remarkable contrast 

 to the form delineated in the preceding plate. In place of the large disk and the simple, 

 stunted, sub-spherical tentacles, we here have elegant ramifying structures of extreme com- 

 plexity that extend a long distance on every side beyond the peripheral border. Both species 



F 



