52 



reasons which have led me to adopt the notion that such a non sexual propagation does at 

 times actually take place in the Brisinga. 



There is one thing which must immediately be remarked by any one who has exa- 

 mined a sufficient number of specimens of this form; and that is the frequently vevy une- 

 qual development of the arms or rays. In nearly all the specimens examined by me one 

 or more of the arms, and sometimes even most of them, proved to be in a more or less 

 rudimentary state, and evidently only quite recently regenerated from the disc. That these 

 newly formed arms had grown in the stead of fully developed arms which had been sepa- 

 rated from the disc, was evident from the structure of the disc, and admits of no doubt. 

 The question is now to explain in a reasonable manner the so frequent detachment of fully 

 developed arms in the Brisinga. To assume that such detachment is caused by accidental 

 external violence, or hostile attack of larger sea-animals, might certainly be admissible if 

 the question was only of isolated cases. But where the occurrence proves to be so frequent, 

 as my investigations have taught me, that it may even be considered as the general rule, 

 while it is the ^exception to find specimens with all their arms equally developed; I should 

 be more inclined to recognise a more normal phenomenon, namely a real voluntary act of 

 the animal, a spontaneous detachment of one or more of its symmetrical principal parts 

 (Antimera) that is to say a peculiar sort of division, the object of which is to effect 

 a non sexual propagation. To state briefly my opinion, I think that every arm thus detached 

 does not perish, but is destined to form a new individual by reproducing from its adoral 

 extremity a new disc, which then, by a sort of budding, sends forth the other Antimera 

 or arms belonging to a completely developed individual. I think I may be allowed to as- 

 sume the possibility of such a propagation, when we consider the great self-substanciality 

 of the arms of star-fishes generally, and especially of those of the Brisinga; and likewise 

 that direct observations are not wanting which appear to prove that such regeneration may 

 in isolated cases take place even in much more centralised star-fishes, for instance in the 

 genus Asterias and Ophidiaster. 



3. Faculty of regeneration and tenacity of life. 



That the star-fishes possess an extraordinary power of regeneration is sufficiently 

 well known. This is especially easy to ascertain in the forms that are found in the litoral 

 belt, and therefore exposed to many external injuries, often bearing the marks of the most 

 diversified damage, which yet does not appear to have any appreciable influence on the 

 vital vigor of the animal. From the injured parts it may be observed that a very lively 

 new formation takes place, whereby not only the woimded surfaces heal rapidly, but also 

 the lost parts, with all the organs belonging to them, are in a shoi'ter or a longer time 

 completely regenerated. In the deep-sea star-fishes it is however much more rare to find 



