38 LESLIE B. AREY 



Parker and Haswell ('10) in their ''Textbook of Zoology" 

 refer to the more or less upright position which Amphioxus as- 

 sumes after burrowing in sand and then add the following 

 astonishing and somewhat ambiguous statement (vol. 2, p. 46) : 



"It also swims in the vertical position, ." However 



this assertion may be interpreted, it certainly is contrary to fact 

 as far as the West Indian Amphioxus is concerned, and from the 

 description of other writers (see also the frontispiece in Willey's 

 '94 book), the same criticism undoubtedly applies to the closely 

 allied European species as well. Anyone may easily convince 

 himself that the foregoing quotation either presents a gross 

 error or is highly misleading (according to the alternate possi- 

 bilities of interpretation), if he will observe for a short time the 

 locomotor responses, regardless of the antero-posterior orienta- 

 tion, exhibited by Amphioxus under various natural or experi- 

 mental conditions. 



While working recently at the Bermuda Biological Station 

 opportunity was afforded me for making observations on the 

 swimming habits of the West Indian lancelet, Branchiostoma 

 caribbaeum Sundevall, a species verj^ similar to the common 

 European Amphioxus. This animal is found in abundance 

 in the coarse coral and shell sand of Flatts Inlet, which connects 

 the water of Harrington Sound with the outside ocean. 



Ordinary mechanical stimulation, as by a finely drawn glass 

 rod, gave too active a response for observation and accordingly 

 a milder stimulus was sought. This was found in a weak stream 

 of sea-water forced from a rather large canula; if the jet was weak 

 and was directed vertically through 10 cm. of air and 10 cm. of 

 water, the entire body of the animal became subjected to a 

 gentle stimulus formed by the wave front. When thus stimu- 

 lated the locomotor response tends to be less energetic and the 

 disadvantages of local or directional stimulation are obviated, 

 while it has a further advantage over other mild stimuli such as 

 jarring the containing-dish, inasmuch as individual animals 

 may be singled out for experiment and watched from the begin- 

 ning of their course. 



