ca) 
oO 
twenty-gram rock bass may be fifty to one hundred times more resistant 
than the most sensitive stage in the egg or fry. This might be a safe 
guess for shrimps also. To meet Illinois problems alone, there is imme- 
diate need for a study of the entire life-cycle resistance of the suckers. 
Choice of Stages to be tested and Frequency of Tests—The early 
stages should be tested at very short intervals. Artificially fertilized eggs 
should be divided into lots and tested at intervals of fifteen minutes to 
several hours (Child, ’15, pp. 412-416). 
TABLE IT 
Showing differences in sensitivity of various stages of several marine and 
fresh-water animals. Most sensitive stage rated as 1. No basis for a comparison 
of the species. Whitley’s results are not comparable with those of the others, as 
his experiments showed only abnormal development. 
Species Poison Gee oe Observer 
| 
SSPATIISIN 2) oi ekeleisiee)< KCN Unfertilized egg .......... 9.00 
Blastula to gastrula...... 1.00] Child (’15) 
Young bipinnaria ........ 2.00 
Sea-urchin....... KCN Unfertilized egg .......... 3.88 
i Barly. pastrula: © sie. iie:s's.s 1.00 Gs ot 
CER EDLILCTIS: a5 o'eccts cies bie « 1.50 
Clam-worm....... KCN 2% COM STAZ CS le bie icvess mneie a's 18.00 
Larva with 2 pairs of setae 1.00 se tC 
Advanced larva .......... 3.30 
KAD ASH 2 skh sh Phenyl COMP SCAR EGs empire sccieinteucte ot 6.00 a a 
urethane | Hatching ................ 1.00 
Tautogolabrus....| Phenyl | 15 min. after fertilization. 43.00 » 
urethane | Heart beating ............ 1.00 S 
Newly hatched ........... 1.25 
Plaice eggs....... Acid TURE <SRes neOone goes 1.00 | whitl 05 
Acid |10daysold............... 10.00 ey C88) 
Plaice eggs....... Alkali WIEST AA ciieretats.cise ers. s oe 1.00 “ “ 
Alkali MOM GAY SH OL Sere entice ,cces oh) 2/0 2.00 
Rock bass........ CO;and) WMeSveramieis ys Jf 05 0's 2s 1.00 | ‘ 
lowO, | 20-40 grams ............. 5.00| Wells (18) 
Common shiner,....|) CO;and /0:6oeram o.0.6 65. ose. cess 1.00 | Ge a 
low O, DAGON EP LAMIS hope petayatale cheng sites. « 3.00 | 
Concentrations and Time to Death—Tests should be made on each 
stage with five concentrations of the poison. Time-concentration curves 
should be plotted, reciprocal curves constructed (Krogh, ’14; Powers, 
18), and the comparisons made should be based on concentrations within 
which the rate of killing is regular. 
