68 EMBRYOLOGY OF THE STAEFISH. 



tirely different characters from the Bipiiinaria of Miiller. Judging from 

 the development of our Starfish, it seems to me that Miiller's Bipinnaria 

 von Helsingor, second Memoir (PI. I. Fi(js. 1-7), is probably nothing 

 but a younger stage of his Brachiolaria von Helsingor (PI. II. Figs. 4, 

 5; and PL III.). Van Beneden's Brachina, in its turn, is a still younger 

 stage of the same thing, or of an allied species. A comparison of the 

 above figures of Miiller, and of the figures of PI. III. of this Memoir, 

 will leave no doubt on this subject. For the same reasons the Brachio- 

 laria of Marseilles is probably only the adult of a Bipinnaria, closely 

 resembling that of Marseilles (second Memoir, PI. I. Fifis. 8, 9), if it is 

 not the same species. In the Brachiolaria figured on Plates II. and III. 

 of the second Memoir of Miiller, the young Starfishes are evidently on 

 the point of resorbing the arms. The larvae present all the appear- 

 ance of contraction and distortion usually accompanying this process, and 

 Miiller's figures agree entirely -with the various attitudes which they as- 

 sume during this resorption. 



If we now turn to his fourth Memoir, which contains the fullest de- 

 scriptions, we shall see that although in many of the figures of Miiller 

 the Starfish, or at least one side of it, has been drawn correctly, yet his 

 statements and some of the figures wliich he gives cannot be reconciled 

 with one another. On Plate II. Fi(js. 5, 6, of his fourth Memoir, we 

 have the evidence, from his own drawings, that his Bipinnaria had two 

 water-tubes ; yet, in the subsequent stages, Miiller says positively that 

 it has only one water-tube, the one with the water-pore, — a statement 

 entirely contrary to the earlier stages of his Bipinnaria. From what I 

 have shown of the mode of development of these water-tubes, of 

 their increase in size in proportion to the age of the larva, it is quite 

 improbable, notwithstanding the statement of Miiller, that one of them 

 should disappear ; he also says that they are not to be confounded with 

 what he calls " wimpernder Schlauch," while our observations of Astera- 

 canthion go to show that these two systems are but one. 



The discovery of the water-pore in Miiller's Bipinnaria was a great 

 step towards solving the question of the origin of the madreporic body, 

 which he rightly conjectures to be nothing but the water-pore. He also 

 notices the rosette of tentacles, or, more properly speaking, the five radi- 

 ating tubes from which the tentacles eventually branch. He fails, how- 

 ever, to notice that this rosette, like the cap of the Starfish, as he calls 



