ECOLOGICAL SUCCESSION. 1| 



in the spring it- place i- lakc-n by iu-\v vegetation a- rapidly 

 as the decomposition of the old takes place. 



Prom our knowledge of the composition of river water in- 

 habited liy all the fish, before and after the Hood-. IK. -real 

 importance could be assigned to mineral-, even though the com- 

 plexion ot the analyses changed with the season. However, no 

 positive ' onclu-ion could be drawn without careful stndv of 

 the ln'hin'inr n-nctions of fish to minute quantitie- of -alt. 



'/ Gas The results of gas determination are -i\en in 

 Table- IV.. \'., .md V|., pp. 5 and 6. Table- IV. and V. -ho\\ the 

 '"iitent ,f the open water, abo\ e the xe^etation and -andv 

 bottom, to be -ulticient for fish in all the pond-. Jndav and 

 liir^e. 'n. p. iv>. state: " Konig found that he could keep ti-h 

 'kind not -pei ilied i in water which contained j.o.S C.C. and i j8 

 ol di--o|\cd oxvgcn per liter without any apparent ill et!< . ts. 

 'I horner loimd that a fish epidemic \\a- i .m-ed by the ab-ence 

 of free oxygen. I loppe-Seyler and 1 >mx an -t.tte that trout \\ hich 

 \\ere kept from one and a half to t\\o and a quarter hour- in 

 \\aier ha\iiiL; <>nl\ Irom o.cjN to 1.71 c.< of o\\-eti per liter 

 shoued marke.l -uiis of dyspmra. r.itoii. in experiment- -MI 

 young i.iiubou in. i it, found that a fall in tin- amount of di >\\ e. 1 

 o\\-en be|o\\ one third of the normal amount, /'. e. t belo\\ j 

 per liter ol \\atei. is prejudicial and geiieiallx fatal. Some indi- 

 \idn.il- ho\\e\er, \\i-re able to sustain life l.-r lon^ period- in 

 \\atei \\hich (oiitained only minimal tr.ue- of <li--ol\ed oxygen. 



" l\ nau i he I ou! id that carp kept for an hour and twenty minuie- 

 in \\ater \\hich i . .ntained 1.33 c.c. "i o\\-en per liter, did not 

 sh.\\ an\ -i^n- ol dyspild-a, \\hile other- became d\-pno-ic in 

 \\atei containinv; from 2 c.c. tt) ,V I C.C. of tin- gas." 



I'.ii'^e and Juday state also that Mat kin, lu tn.ut ha\e been 

 taken tiom \\ater> with I C.C. per liter. Ti-h di-ea-e- .ti\ -aid 

 to be nion- pn-xaK-ni in low o\\-eii i oim-ni Knaiithe. '07 . 

 In thi- case I here is no reason for a--i^ninu importance to the 

 Oxygen content of the open \\ater- frei|iiented b\ ti-h. and this 

 factor i- nearly uniform in the different pond-. The oxyj 

 con t i'n t of the Lot torn i- of great import a IK e and u ill be di-cii- 

 laler in connection with breeding. 



Temperature. A -in-le -el ..I reading- taken in the late 



