INTERNAL ANATOMY OF A STAR-FISH. 123 



tween them. " There are no distinct respiratory organs, but the surfaces 

 of the viscera are abundantly supplied with cilia, and doubtless subserve 

 respiration ; the sea-water being freely admitted into the general body- 

 cavity by means of numerous contractile ciliated tubes, which project 

 from the dorsal surface of the body " (Nicholson). There is a nervons 

 system, also, in this apparently immovable and insensible denizen of the 

 deep. A gangliated cord surrounds the mouth, and sends filaments out 

 along the centre of each arm to the little red speck discernible at the tip, 

 which is an eye. How well they can see with these eye-specks is unde- 

 cided, but there seems no doubt that they can perceive obstructions in 

 their path, for they begin to get ready to mount them before actually 

 striking against them. 



The mouth, as I have said, is a mere circular opening without teeth. 

 The stomach is reached through a short gullet, and of itself is not large, 

 so that it is difficult to understand how the results of the tremendous 

 gluttony for which this fellow is famous can be accommodated until we 

 open him, and find that, as a part of the stomach, loose yellow pouches ex- 

 tend far into each arm, filling up much of the interior of the rays. When 

 no great meal is to be eaten, these pouches or cwca are not brought into 

 use; but when occasion arises they can contain a surprising quantity. 



On the floor of each arm we have dissected is seen the ambulacral 

 ridge, upon either side of which are the vesicles that supply the foot-ten- 

 tacles, which may be filled or emptied at the pleasure of their owner. 

 Above these, occupying the most of the interior space towards the end 

 bf the ray, and also appressed between the caeca and the upper surface 

 towards the centre, are the grape racemose masses of the generative 

 organs. 



Few persons, probably, suspect that in so low a grade of beings the 

 sexes are divided, yet this appears to be the case in the star-fishes. Ac- 

 cording to Prof. Alexander Agassiz, the males and females of our com- 

 mon species of star-fish can readily be distinguished by their difference in 

 coloring : all those having a bluish tint being invariably females, while a 

 reddish or reddish-brown color indicates a male. "When cut open, so as 

 to expose the genital organs, the difference between the males and females 

 is still more striking. The long, grape -like clusters of reproductive 

 organs, extending from the angle of the arms, on both sides of the 

 ambulacral system, to the extremity of the rays, present very marked dif- 

 ferences in the two sexes. The ovaries are bright orange, while the 

 spermaries are of a dull cream color. At the time of spawning . . . the 

 genital organs are distended to the utmost, filling completely the whole 



