Hyalella Knickerbokeri 243 
copulation takes place which usually occurs during the next twenty-four 
hours after the female moults. Oviposition then follows copulation 
directly and the female breaks away from the male’s grasp either 
before or during oviposition. 
SEASONAL DISTRIBUTION OF NUMBER IN Broop. 
Preliminary measurements indicated that the third joint of the 
peduncle of the second antenna is in direct proportion to the length, 
which in turn has a direct correlation with the age of the animal. I 
Sy SEESESRE Es bees ree cect eee] cocoa’ coast ees cores creer COEETESIET pay + 
mee aeee ee Geaeeee = 
Sede seget eae e gered eer eres ae cee 
SS ee es sept omen eee eee nes ete reese pies 
See ee ee ar eter tc ct ete ae ele 
He Cpe eel le et Sa nm Cte ete ete ed oe ru Can sete FO Es cE ae 
rier ieeteesgsetsecteaeeetes pesca seg eeeeegeeieee a eeee eet eete = Pag 
ede cesfoseeeedees tee stendee pete eed pee ees poe] 
Sgt Greet let eps ae Foe near oe oar ce ee evita 
Gees cee eceeteestaee SESESCEY cenercetceeepeemesae ae i : Seneeneened 
esse eget eeeete ee eee tetanus ested eps 
See ened ees eae ee a = ne eesti 
ne Pare ee ieee 
a i 7 
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} 
SEH 
inert 
EHTEL EE 
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44 aware FLY 
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seceed 3 
At I 
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rH sen cers } Herrat 
tH + VRaOGD Ready 
wwe F| ia 
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EERERELE 
zt 
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tT a8} Ehret 
f 
tert 
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mauegenal sas 
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He EE 
eS Eanes 
Huan aati Gate Ey ee 
i ee sere Beare aehe d Hert 
eee ese sieceeg cui eesetieedecd ey 
cag sso cieteeteateieuhaueneeaeened 
arent dee seneat 
pasiatieiteniersteneates : 
HEEET EEE fore eee! euttazas erie ie FTeH 
fesseesteeteaseers respecte 
esveeieeted 
aeeae cna 
gee 
Figure 3. Shows the transition period between time represented 
in Figure 1 and Figure 4. The time broods were extruded was August 
7-14. 
