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26O 7W OCEAN WORLD. 



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thoroughly investigated. The vascular apparatus is sufficiently deve- 

 loped in these Echinoderms, and appears to have for its centre an 

 elongated canal with muscular walls, which may with some justice be 

 honoured with the name of heart. A little ring surrounding the 

 oesophagus, and from which issue certain delicate white cords, which 

 are prolonged into the furrows of the arms, presents us with all that 

 can be designated a nervous system in the star-fishes. Among organs 

 of sense we may, perhaps, mention, as being sensible of touch, the 

 tentacular ambulacral feet. The eyes are considered to be certain 

 bright red points which are situated at the extremity of the arms 

 almost on their under surface a most singular position for the organs 

 of sight. The eyes must, however, be very imperfect, for they possess 

 no crystalline lens. Ehrenberg insists upon the existence of eyes 

 in some species, attributing the function to those red spots, however ; 

 while Rymer Jones attributes the indications of sight-seeing sometimes 

 observed to an extremely delicate sense of touch in the star-fishes. 

 Professor Edward Forbes, while he admits the existence of ganglions 

 in the nervous system to be extremely doubtful, seems, by the frequent 

 use of the terms eyes and eyelids, to admit that the specks in question 

 are visual organs ; the weight of authority inclines therefore to Ehren- 

 berg's view, that if not eyes in the strict sense of the term, they serve the 

 purposes of vision, modified and adapted to the wants of the animal. 

 The star-fishes have distinct sexes, with individual differences ; 

 their eggs, which are round and reddish, undergo curious phases of 

 development. They produce little worm-like creatures, covered 

 with vibratile cilia, like the Infusoria, which swim about with great 

 vivacity ; these little creatures are subject to considerable changes. 

 In the year 1835 M. Sars described, under the name of Bipinnaria 

 asterigera, an enigmatical animal resembling a polyp from the arms 

 at one extremity of the body, while the other terminated in a tail, 

 furnished with two fins ; but it was chiefly remarkable as having an 

 Asterias attached to the extremity which carried the arm. He 

 expressed an opinion, which was soon placed beyond any doubt, that 

 this bipinnaria was an Asterias in its course of development. The egg 

 becomes a sort of infusorium, the infusorium becomes a bipinnaria, 

 and this produces the Asterias. In short, the Bipinnaria does not 

 become an Asterias by any metamorphosis analogous to that so well 

 known amongst insects the butterfly, for example but becomes, so 

 to speak, the foster-mother or nurse to the Bipinnaria. The larval 

 form is large, and it is at the cost of a very small internal rudiment 

 of this larval form that the Asterias is developed : the Asterias robs 

 the larval form of its stomach and intestines, and turns it into a 



