SPONTANEOUS MOVEMENTS IN LAR\VE. 409 



ieure provenant du sang, et determinerait ou favoriserait du 

 moins les mouvements du foetus." 



Wintrebert ('14) states that in the trout the embryonic 

 contractions are more frequent and lively in a medium containing 

 COo than in one containing oxygen. He considers ('20, pp. 450), 

 ihcse movements favorable to respiration, excretion, and circu- 

 lation. He also states that lack of oxygen depresses the move- 

 ment (in Selachians). 1 



I ..[irrimrni in- with cat fetuses eight to nine centimeters long, 

 T. C.raham Brown ('14) observed that rhythmic alternating 

 movements of the limbs (interpreted as progression movements) 

 arose spontaneously and could also be produced by asphyxia 

 re-ul i in- I mm pressure on the umbilical cord. 



In adult animals, the relation between the respiratory center 



and ( < >.j ha- long been known, even though the exact mechanism 



'ill in doubt. Stimulating effects of asphyxial conditions on 



blood i ut ->ure and motor mechanisms through the spinal coid 



have been reported (Mathison, '10 and '11). 



A. I). Waller ('96) found an increased irritability in nei \ e 

 liber- treated with CO 2 , the effect varying with different con- 

 centrations. Roaf ('12) showed that the rate of branchial 

 movements in fish showed a positive correlation with the Il-ion 

 eoi ]<! it rat ion and with the concentration of CO^; the append. >. 

 oi b.irnacli-s showed a negative correlation to these condition:-. 



Thr-r observations and other well known physiological studio 

 indicate that -t imulation by metabolites occurs in many different 

 varieti< - <-l contractile and transmissive mechanisms; it, there- 

 fore, may be expected that alteration of body fluids with 

 respecl to respiratory conditions may have some relation to the 

 endogenous movements of embryos, and in fact it is possible 

 that i han^es in such conditions may be the most important 

 factors in the production of these movements. 



The experiments reported in this paper were undertaken in 

 order to te-t the effect of different concentrations of COa in the 

 -ea \\ater on the spontaneous movements of larva? of Opsanns tan. 



The yolk sac, with the network of capillaries over its surface, 



1 So far ax hi- descriptions go, the depression of movements which he observed 

 .irs tn h.ivr t.iki-n place under asphyxial conditions and were probably due to 

 thf ; action of a considerable excess of COz (\\'iiitrrl.. it, '20, pp. 324 and 



328). 



