CONTENTS 
ARTICLE I.. THE NORTH AMERICAN SPECIES OF THE GENUS 
TIPHIA (HYMENOPTERA, ACULEATA) IN THE COLLECTION 
OF THE ILLINOIS STATE NATURAL HISTORY SURVEY. BY 
Be eA AAG Heo GL GATS) COMORES WONG. <= 9,0 + «see's wri d:01 ¥lainloassievs) « 
LN GREC CO ELNNIC ERO Tide Ntat aoe enetaMars ter icles Se ocae se lateyona\s. oe royale yah ata ols Joi0: pid aa:eoo) ole plain cess 
EVES MOLMATIC ICH ctrcte tei tna elena) scl folererey nie ot ciatsielslaiayalicta « «,/0°aiaye10 ses) asi wathensese 
Gen GM Cw GUATACEOUG tr. tierce raiclcts tel ccoaicicin<susvelt levee) obi je,01. 6 Siaje esis ores Sielsceletere 
PC SVet OUNCE ICH | aT O MVS TOY CUELILOM: ope. eissmivl x70) ecena ates iz w,&) 005.4, sfepmialevela died, ialelerns 
MENELINCLOMMOMENDECIEN op raaiearaies acne elsseea acaragel visto ma © 6yeiein ae (6, se lete, o/s, @ she)a (aie 
ARTICLE II. WAYS AND MEANS OF MEASURING THE DANGERS 
OF POLLUTION TO FISHERIES. BY VICTOR E. SHELFORD. 
SEIMEI MM CL ean eNatet <r. teecta ts are ai et state afagstataral syetciale ci sterela\eltivce'eleletosaie asus 
UEC OM MCI O Tin tre eee olor clea levee m ket aisahe tees tvs elelelclg ons cidhicleleisl\suale's\euwie,w ate wells 
Nine crucial questions in connection with problems of pollution in 
relation. to useful aquatic animals... 0... .c.e ese ccc canes censsees 
I. Is the animal used in testing the toxicity of a polluting sub- 
II. What is the most sensitive stage in the life history of the test 
III. When is the pollution most concentrated?...............--+++ 
IV. What is the toxicity of untreated polluting effluents; of each 
residual of processes of partial recovery; or of treatment by addi- 
VII. If the supply of useful animals is depleted will recovery be 
MENTS ODES OVOr eke sateen ete tehate occa apsen, Fave alle) node ee, alteiel a jeveke eel ae. on le ars) aha, tie 
VIII. Can correct decisions be reached without investigation of 
ingivignel wCASeS a Whi Ch: ATISG 2.5 soe): 2m <si9.5 (els a)'0 sleye ole w eee, olete cial 
IX. What is the real value of the waste when the amount of the 
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