SPONTANEOUS MOVEMENTS IN LARY.K. 4! I 



tering" movements of the body which alternate with irregular 

 intervals of rest have now become regular undulating vibrations 

 which cause short bursts of swimming movements of the fish 

 through the \vater. 



It is evident that the spontaneous movements of the embryo 

 are gradually elaborated into the swimming movements of the 

 larva. Similar bursts of motion at the end of conndcrable 

 interval- of re.-t on the bottom are characteristic of the adult 

 throughout it- -hu; s r ish existence. In the other teleosts which I 

 have observed Fundulus and Tautogalabus], the embryonic 

 movemeiit- occur with much greater frequency and with only 

 \< iv brief intervals between; during development these move- 

 ment- bcioin.- merged into the continuous type of movements 

 ch.iraeter: fishes of pelagic habits. It would appear that 



i lie activity habits of these animals are not widely different at 

 an\ stage of their existence, and are determined by some internal 

 ph\ al mechanism, the earliest expression of which is 



loiind in the spontaneous movements of the embryo. 



Spontaneous movements of the mandible and branchial 

 inei-li.iiii-iii be;.in soon after hatching; they are, at first, slight 

 and irregular, but gradually, in the course of about 5 da\>, 

 tin \ <] -\elop into the respiratory rhythm. Kxteroceptive and 

 piopi i.i. rptive reaction mechanisms do not respond to external 

 -tiniuli at tin time of hatching but gradually become functional 

 during the lar\ al period. 



I'rcliininaiA experiments were carried out in the summer of 

 j'ljj at the Marine Biological Laboratory at Woods Hole. 1 

 .\e\\ly hat. lu-d larva? were exposed to sea water from which all 

 th. were \ .moved by passing hydrogen for an hour and a 



hall through -.a water which had been previously boiled. 



< M i^ specimens, under these conditions, 1 1 -ho \\txl a de> 

 in -pontaneMii- movements. In another set of experiments 8 

 lar\.r \\civ exposed to sea water in which a number of Fundulus 

 had been alloued to remain until they sho\\cd >igns of a-phyxia- 

 tion; ot the-e, o -pecimens showed a decided increa>e in spon- 

 tancoii- nii)\ einents. In another experiment, 6 specimen- \\ire 

 l>laced in l\("\ ;/ 1000 in sea water. In all of the-e specimens, 



1 "I In- i the Marine Biological Laboratory was supplied me from 



tin- liraduatt- K. uul of the University of Kan 



