H8 ACTINIARIA 



The structure of the papillae, named by me "Halcampa-papillae" has never been subject to a closer 

 anatomical examination. In English and American literature they are simply called suckers, a name also 

 used for several heterogeneous differentiations of the column. On closer examination the papillae of Hal- 

 campa duodecimcirrata are found to be completely differing in structure from the verrucae of Urticina and 

 other Cribrinidae. To the scapus of Halcampa, Paraedwardsia and other forms provided with "Halcampa- 

 papillae", greater or smaller numbers of grains of sand most often adhere. After having loosened the grains of sand 

 we find on closer inspection that the ectoderm of the papillae is differentiated from the other parts of the 

 scapus ectoderm. The figure 8, PI. 4 shows a transverse-section through a piece of the outer part of the sca- 

 pus of Halcampa duodecimcirrata with a papilla (only the ectoderm (ec) and part of the mesogloea (me) are 

 reproduced, the section is stained with iron-hematoxyline) . The ectoderm is rather high between the papillae, 

 but considerably attenuated towards the papillae. The outer parts of the ectoderm cells contain numerous 

 grains. In the papillae the ectoderm is wholly transformed. Between the mesogloea and the thick cuticle 

 we see on the section bundles of fibres (ch), rather strongly stained, radially arranged and separated from 

 each other by, as it seems, fairly large intervals. The fibres connect the mesogloea, forming off-shoots with 

 the outer, darker part, the cuticle (c) ; they are not always distinctly limited from the mesogloea. The inter- 

 vals are probably only seemingly cavities, I have sometimes found several intervals to be more or less filled 

 up by granular cells (gl.). I have also observed that these cells easily get loose and are torn off from their 

 original position by sectionizing. As to the cuticle it is of a rather loose consistency, on account of its being 

 stratified. The main part of the cuticle is strongly stained on the reproduced section, in the outer, more 

 faintly stained part, we, however, observe that the cuticle forms several irregular lamellae, which stand out 

 more distinctly when the cuticle is unstained. These layers are incrusted with foreign bodies (in). 



For the sake of comparison I here reproduce two sections through the scapus of Paraedwardsia 

 sarsii and Scytophoms antarcticus. In both species the scapus is provided with a distinct cuticle which is 

 thicker in the papillae than in the other parts. The figure 7, PI. 4 shows a papilla of P. sarsii with adjoining 

 parts of the skin. The section much recalls that of Halcampa. The cavities of the ectoderm are, however, 

 smaller, the bundles of fibres thicker. The cuticle is incrusted with foreign bodies forming a very thick layer 

 in the papillae. The figure 6, PI. 4 representing a transverse-section of one part of Scytophoms antarticus 

 looks a little different. The cavities are large and contain cells, among others large mucus-cells (gl.), the 

 bundles of fibres are shorter, and the mesogloea reaches further on towards the cuticle than in the other 

 forms. In spite of this, there is no doubt that also here we have to do with "//a/cm/>a-papillae". 



How are we to explain these papillae? As far as I can see, these organs are secretory papillae, for 

 which suggestion the circumstance also speaks that the grains of sand are not strongly attached to these 

 papillae, while they are only with difficulty loosened from the verrucae (sucking warts) of for inst. Urticina. 

 The secretion by which the grains are attached is, everything considered, formed by the granular cells en- 

 closed in the intervals, while the fibrous bundles may be chitinized supporting cells, partly fused with the 

 mesogloea. 



Among the specimens of Halcampa arctica I found a specimen without incrustations. I at first sugge- 

 sted that this specimen did not belong to this species, but a closer examination of some sections proves that 



