; '; '-,:-' ' -:: : -V- . ' BIOLO<3\ 



' E.' A. ANDREWS. 



The specimens taken in June were larger, often sexually mature, 

 while those taken later were generally immature or larval forms. 



In captivity they live like the European lancelet ; occasionally 

 leaving the sand and swimming about with considerable velocity, 

 but soon falling to the bottom and resting upon one side as if ex- 

 hausted or else burrowing instantly into the sand within which they 

 move about with great celerity. As long as the water be pure they 

 rarely leave the sand in the daytime and then quickly return when 

 stimulated to motion by a slight touch or jar. 



In flat glass dishes without sand they arrange themselves with 

 reference to light in a manner suggesting that we have here amongst 

 these simple, eyeless vertebrates an example of heliotropic movement 

 such as plants and many non-vertebrates exhibit. At the end of 

 some hours of alternating periods of active locomotion and lethargic 

 rest most of the individuals are found collected upon one side of 

 the dish, that furthest from the light. 



The same distribution ultimately results when the dish is turned 

 through 180. When carried to the door of the laboratory and 

 exposed to the direct rays of the sun a most violent commotion 

 immediately followed and soon ^resulted in the collection of all the 

 passive individuals upon the side of the dish most remote from the 

 source of light. 



Finally when the dish was placed in the centre of a small square 

 room lighted by a window on the north and one on the east and 

 either window opened, the animals collected in the part of the dish 

 most remote from that window. When both windows remained 

 open the position of the lancelets was vaguely that part of the dish 

 most remote from both windows. 



As far as these experiments go they may be taken to indicate 

 that we have a case of negative heliotropism in these simple verte- 

 brates : that the lancelets move away from the source of light along 

 the direction of its rays : that the directive action of the sun's rays 

 is as in the numerous non-vertebrates studied by Dr. J. Loeb. 



Though small, the largest not exceeding a length of 16 mm., 

 many were sexually mature, yet individuals kept for many weeks 

 did not discharge ova, except in one collection taken early in June ; in 

 this case some of the ova were naturally fertilized and a few developed 

 as far as the gastrula stage, when they were destroyed by an accident. 



