ECHINODERMATA. 267 



considered to be certain bright red points which are situated at the 

 extremity of the arms and on the under surface a most singular 

 position for the organs of sight. The eyes must, besides, 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 Eymer Jones attributes the indications in 

 which this originates 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 eye and eyelids, to admit that the 

 specks in question are visual organs ; the weight of authority inclines 

 therefore to Ehrenberg'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 develop- 

 ment. They produce little worm-like creatures, covered with vibratile 

 hairs, 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 enig- 

 matical 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 bipiiwaria was an Asterias in 

 its course of development. The egg becomes a sort of infusoria, the 

 infusoria becomes a ~bipinnaria y and this produces the Asterias. In 

 short, the Bipinnaria does not become an Asterias by any metamorphoses 

 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 larva is large, and it is at the cost of a very small 

 internal rudiment of this larva that the Asterias is developed : the 

 Asterias robs the larva of its stomach and intestines, and turns it into 

 a visceral apparatus for its own use. But the Asterias makes itself a 

 mouth of any of the pieces most remote from the primitive mouth of 

 the larva. Thus the Bipinnaria divides itself ; it gives its stomach and 

 intestines, and keeps its oesophagus and mouth, and it can live several 

 days after the Asterias is detached from it. 



