55 



a. Early Stage of the Brisinga. 



From the same locality whence I obtained my supply of Brisingas, I once chanced 

 to get out of the mud brought up in the dredge a little tiny 10-armed young star-fish 

 which, in spite of its very different appearance at first sight, may nevertheless with full 

 certainty be classed as a Brisinga in a very early stage of development, exhibiting in more 

 than one respect points of very special interest. 



The specimen (Tab. IV, fig. 38, 39) has only a disc-diameter of 2.50 Mm., and has all 

 its arms 10 in number in natural connexion with the disc. The length of the arms cannot 

 accurately be ascertained; as in all of them the extreme point is broken off. They do not 

 however appear to have exceeded in length the double diameter of the disc. Now what 

 immediately appears remarkable in them is that they proceed from the disc apparently 

 quite in the ordinary manner like simple prolongations or expansions of it, without any 

 indication on the exterior of any sharp limitation as in the adult Brisinga. Altogether this 

 young animal is in its whole habitus a completely normal star-fish resembling most the 

 young Solaster papposus; and it would not easily have occurred to me that the little animal 

 Was a real Brisinga if I had not noticed in it a peculiarity which induced me to examine it 

 more minutely. Quite unlike the young Solaster, it remained clinging with great tenacity 

 to every object it come in contact with, exactly in the same manner as a Pedicellaster, 

 which already would at once indicate a very specical development of its pedicellaries. On 

 examining the latter microscopically, I found to my surprice that they corresponded even in 

 the minutest details to those of the adult Brisinga, and, as in the latter, a great many of 

 them were crowded together on the skin-sheaths of the arm-spines. A further examination 

 of the specimen brought to light many other characteristics, demonstrating with absolute 

 certainty that we have here really a young Brisinga before us. 



Let us therefore consider this young animal somewhat more closely. Viewed from 

 above (fig. 39) it exhibits, as before mentioned, all the characteristics of a completely normal 

 young star-fish. In the dorsal skin there appear already to be formed various calcareous 

 deposits. In the interior there may be remarked an extremely fine hyaline calcareous net, 

 perforated with regular holes, and here, strangely enough, forming large connected divisions 

 of irregular form. Each of these divisons consists however only of the most primitive cal- 

 careous elements widely different from the complicated calcareous net which is fovmd in 

 developed star-fishes. From these calcareous nets in the skin there issue at regular inter- 

 vals larger and smaller spines, a couple of which were of quite unusual length and extre- 

 mely thin, almost like bristles, but every one enveloped in its separate cuticular sheath. 

 In the angle between two contigaious arms there may be observed a more regularly formed 

 plate, which without doubt is the rudiment of the wedge-plate found here in fully deve- 

 loped specimens. But no distinct trace is yet to be seen of the marginal plates that stand 



