428 ■- OP Tin: AMKKH AN A.CADEMT. 



3 Beat. 



The reactions of amphioxus to heat liave been scarcely more than 



touched upon by tin- aumeroue investigators who have Btodied tin- re- 



onsand habits of this animal As has already been pointed nut, the 



opinion of Rohon ('82, p. 38) and of Kohl ''90. p. L85 . that the light 



stions of amphioxus are really reactions to radianl heat, is erroneo 

 moreover it is in>t to be expected that animals like amphioxus, which 

 live always under some depth of water, would have any special organs 

 lor the reception of radianl heat. Bince rach heat pen water only 



a centimeter or two and hence would almost never reach these form-. 

 The kind of heat that is a factor in the environment of amphioxm 

 the molecular vibration such as we recognize in the temperature of 

 water, and this certainly has a distinctly circumscribing influence on 

 the lancelets. 



In testing the effect of heat on amphioxus, the temperature of the 

 water in which they were living in the Platte Inlet, :;i° C. (July, L905), 

 was taken as the normal, and two series of experiments werecondue- 

 one at temperatures above this and another at temperatures below it. 



When lancelets were transferred from sea water at :!1° ('. to sea v 

 .it 35° 0., they responded by darting about several times and then sink- 

 ing quietly in the characteristic way to the bottom of the dish. Their 

 subsequent reactions were essentially normal. 



When transferred to sea water at :;t° C, they made several quick 

 dart-, and finally fell quietly to the bottom, where they rested. When 

 under these circumstances dilute acid was applied to them, they were 

 found still to be actively responsive. 



When transferred to water at 40° C, they made one or two sudden 

 plunges, after which they dropped to the bottom, while their Bemi- 

 transparent Bubstance gradually whitened. When touched with dilute 

 acid, the animals quivered slightly, but did not react otherwise In a 

 short time they were dead. 



At 42° G. the animals darted once or twice, whitened quickly, and 

 dropped to the bottom dead. Bert ('69. p. 21) state.- that water at 

 41° C kill- aniphioxus in two minuti 



At 45° C. no locomotor response at all was given, and the animals 

 began to whiten at once; they were apparently dead before they 

 shed the bottom of the dish. 



It is plain from these record- that heat has at least two influences 

 on amphioxus It stimulates them to momentarily vigorous locomo- 

 tion, and it also brings about death by the coagulation (whitening) of 

 certain materials in their living substance. The coagulation begins 



