DIRECTION OF LOCOMOTION OF THE STARFISH 29 



In considering the first of these theories we are at once con- 

 fronted by the great comphcations which take place in the meta- 

 morphosis of the stgirfish, and which render extremely difficult 

 the correlation of planes and the orientation of parts in the larva 

 and in the adult. It is true that a number of years ago Goto 

 ('98, p. 241) believed he had proven ''a direct connection between 

 the two principal planes in question, sagittal of brachiolaria 

 and of adult," and "that this connection is that of exact coinci- 

 dence." He beheved his studies made it clear (p. 242) that 



The sagittal plane of the larva cuts the disc of the star at right angles 

 and passes through the water-pore and the centre of the disc, that is 

 to say, the sagittal plane of the larva and the plane of bilateral symme- 

 try of the star are coincident. The arms of the starfish maj^ therefore 

 be justly spoken of as the median ventral, the right and left dorsal, 

 and the right and left ventral, arms. It need hardly be added that 

 the ora 1 side is anterior, and the aboral side posterior 



as they are in the holothurian. 



It is clearly evident that if tliis simple relationship were true 

 it would serve nicely to explain the results on locomotion, since 

 the plane of bilateraUty with respect to direction of crawling 

 practically coincides with that which he believes separates the 

 symmetrical halves of the brachiolarian larva and the adult, 

 at least if we consider the physiological 'anterior' to be in the 

 general direction of arms e and a rather than exactly tlirough 

 a. Later researches have, however, apparently failed to corro- 

 borate Goto's conclusions, the complications of metamorphosis 

 being much more difficult to unravel than would appear from 

 his description, so that we are probably not justified in accepting 

 this as an explanation for the preponderance of locomotion in 

 one direction. 



Similarly, the measurements which have been presented, al- 

 though they appear to show a very slight correlation between 

 mean length of arm and direction of locomotion, would seem to 

 indicate that this explanation too must be rejected. Further- 

 more, if such a correlation actually exists, it will not serve as 

 a satisfactory explanation, for we should still have to account 

 for the proportional relationship of the arms.^- 



1^ Goto's contention, if true, would of course siitisfuctorilv account for this. 



