IN THE DEVELOPMENT OF COMATULA. 243 



instantly closed down over them. In this retracted state it may remain for a 

 long time, wearying the patience of the observer, who may have to wait for hours 

 together before he can again obtain a satisfactory display of its structure. 



The interior of the calyx is occupied by a reddish-brown visceral mass, 

 obscurely visible through the walls ; but I have not succeeded in obtaining a 

 glimpse of the mouth, nor have I been able to discover the anal aperture. 



The stem consists of a column, composed of a pile of segments solidified, like 

 the walls of the body, by the deposit in them of earthy matter, and presenting 

 also the same peculiar reticulate structure. Three or four of the upper segments 

 are somewhat globular or bi-conical, giving a moniliform appearance to this part 

 of the stem, while lower down the segments become cylindrical. Those situated 

 near the middle of the stem have a prominent ridge running round their centre ; 

 while in those nearer the root the ridge disappears, and a simple line takes its 

 place. Indications of a differentiated axis are visible through the whole length 

 of the stem. The stem admits of slight flexure from side to side, and during life 

 the animal may be every now and then seen swaying through a small arc. The 

 whole of the stem is enveloped in a transparent membrane, which is particularly 

 distinct on the upper part, and is a simple continuation of that which has been 

 already mentioned as investing the body. 



The multiplication of the segments in the stem seems to take place by the divi- 

 sion of the pre-existing ones, and this division seems indicated by the transverse 

 ridges which, in several of the segments, may be seen running round the centre. 



In attempting to determine the exact affinities of the remarkable little organism 

 now described, an important question presents itself at the outset : Are we to 

 regard it as a mature form, or only as a transitional state in the development of 

 some other ? Everything tends towards the adoption of the latter view, and I 

 think there can be no doubt that the little Echinoderm now described is one of 

 the early stages in the development of a Comatula. That it had been seen by J. 

 V. Thompson seems evident, from his celebrated memoir on " Pentacrinus 

 Europseus,"* where some of the figures which accompany that memoir appear to 

 be made from an organism identical with that here described, though the want 

 of completeness in the description, and of sufficient detail in the figures, have 

 left this part of the history of Comatula in a very imperfect state. 



Again we find what we must regard as the same organism, figured by Dujar- 

 DiN. This naturalist figures in plate i. fig. 13 of his Histoire Naturelle des Zoo- 

 phytes EcJdnodermes, a minute animal, which he observed at Toulon in 1835, and 

 which he considers as the young Comatula. at the commencement of its stationary 

 existence. I have no doubt that the distinguished French naturalist had before 



* John V. Thompson, "Memoir on the Pentacrinus europseus. " Cork, 1827- 



