70 EMBRYOLOGY OF THE STAEFISH. 



Bipinnaria asterigera of Koren and Danielssen are undoubtedly correct. 

 What they took for a respiratory opening, leading into the cavity, is the 

 mouth ; they had correctly seen the anus, as well as its connection with 

 the intestine of the Starfish. Judging from the figures of Miiller, anu 

 of Koren and Danielssen, there are evidently striking differences in the 

 termination of the intestinal canal, from that of our Starfish. In Bipin- 

 naria asterigera the anal opening is on the abactinal side of the Starfish, 

 while in our young Starfish it is still on the actinal side. The position 

 of the young Starfish, with reference to the stomach of the larva, seems 

 still to require further investigation, as it is not j'ossible to say, from 

 the figures of Miiller, or from those of Koren and Danielssen, what is 

 its true relation, and whether it has the same oblique position which it 

 occupies in our young Starfish. The investigations of younger specimens 

 than those examined by Miiller, or Koren and Danielssen, will at once 

 settle this point, as well as determine the mode of formation of the mouth 

 of the young Starfish, and the question of its separation from the Bipin- 

 naria. From the figure given by Miiller, in his third Memoir (PI. YII. 

 Ficis. 5, 6, 7), I am led to think that the position is also an oblique one ; 

 and that, though the Starfish may separate from the Bipinnaria, yet it is 

 undoubtedly the opening of the oesophagus into the stomach, which be- 

 comes the future mouth of the Starfish, as in our Asteracanthion. In 

 his third Memoir Miiller shows conclusively that the madreporic body is 

 not the scar left by the junction of the young Starfish with the Bipiimaria, 

 but corresponds to an opening leading into a short tube between two 

 of the arms ; and also points out the probability of its correspondence with 

 the opening leading into one of the water-tubes which he had noticed in 

 Auricularia. This supposition is fully confirmed by the observations we 

 have made of the coincidence of the water-pore and of the madreporic body. 

 The slit in the Starfish, noticed by Miiller and by Koren and Danielssen, 

 was probably owing to the fact that in their young specimens the sj)iral 

 was not yet closed and flattened, as is the case in older Starfishes. 



From the drawings of Sars, and of Koren and Danielssen, it would seem 

 as if a large tube extended into the long appendage opposite the arms. 

 If this is truly so, it leaves no doubt that the long, tail-like appendage 

 of the Bijjinnaria is homologous to the brachiolar appendages of our larvae, 

 only developed to a much greater extent, and with all the arms placed 

 nearer together, immediately round the mouth. A comparison, after care- 



