SPONTANEOUS MOVEMENTS IN LARV.E. 417 



It must be stated that there are a few aberrant specimens 

 which fail to react in the usual manner. The number and 

 incidence of these are shown in the tables. Some of these 

 - are only apparent, since most specimens show move- 

 ment either while the bottle containing them is being shaken 

 <>r in the interval (a minute or less) immediately afterward, 

 In -fore the record can begin. These movements, of course, do 

 not .tppear in the record. Also, there seem to be more aberrant 

 -|>ei imi-ii- in the higher concentrations because of the stronger 

 narcotic action of CO 2 and its more rapid onset. Some are 

 ; iaps pathological in spite of careful effort to select only 

 Uhy specimens; there is a large mortality under laboratory 

 <, minions, perhaps 50 per cent, during the larval period. Most 

 of those exceptional specimens are probably thus explained; 

 \\ln -i her all can thus be accounted for, is uncertain; there may 

 be plr ical conditions in which an increased CO may 



produce a depression immediately instead of stimulation. 



B. Rate of Respiratory Movements. 



In the lower ranges of concentration of CO, the respiratory 

 rate is faster during the period of exposure (Charts VI., \ II., 

 YIII.). The middle ranges of CO 2 concentration (Charts IX. 

 and X.) appear to result in a balance between the stimulating 

 and depressant effects. In the higher ranges (Chart XI.) after 

 a short period of stimulation, the rate falls considerably below 

 the normal. In the extreme concentrations (addition of 3.5 per 

 [.-4 per cent, acid to the sea water Chart XIY.) the respi- 

 ration U< i 'i nes irregular, then of the Cheyne-Stokes type; after 

 a time it gradually improves and becomes regular, though 

 proci-dinu .it a somewhat slower rate than in the normal. Reuss 



io h.is >ho\vn the stimulating effect on the respiratory rate of 

 moderate c< mcentration of CO 2 in adult fish and the depressant 

 t it. i i 1. 1" higher concentrations. There is, therefore, a tendency 

 for tlu>e higher concentrations to break down the respiratory 

 em; the capacity for recovery is probably dependent on 

 secondary reserve mechanism. This capacity for recovery 

 not to be possessed by the spontaneous movement-. 



< >n return to normal sea water, the effect of the lower con- 

 ivnirations (Charts VI.. YII.) is the same on the respiratory 

 rate as on the movements, that is, a depression below normal; 



