519 
RELATIVE NUMBER OF SPECIES IN THE PLANKTON OF QUIVER CREEK AND SPOON 
AND ILLINOIS RIVERS. 
| 
| 
Quiver Spoon Illinois 
Group Creek River River 
Algae—totalsinccncctscsmanties caer. 5 Bott 25 | 34 74 
ChIZOph YC 3.52 s1s.ceisis, « simis-s fee Boracisse I 4 Il 
GChloxrophyces en-route sce: oncecsices I I 3° 
BaellariaGes an. cme acuciesis seeerieee ees 20 14 2 
Conjugate | femecse veri 3 5 
Protozoa —totals ..... ue Roa “18 63 = 154 ‘s 
Rhizopoday: sr. scat smenenneciess a08 13 17 3° 
BE OzOals. ecw | paertc nae ee en iasektnear fe) fe} 4 
Mastizophorarrccconeern aatcoinenn 5 28 62 
Ciliataet leodacor co heeeicen ces eoeeleaes oO 16 55 
SIGHT Goo ceo Doo end sduEn deaGene. de fe) 2 | 5 
Rotifera— totals <celcceciees ces oe Seite II 44 107 
RDI ZOtay ne coats celocee moses nee ecr I I 6 
Bdellgidary sae ene season eneeeee 3 4 6 
PU Gia easter sais terceicle eae cereals totstaee eae 7 39 95 
Crustacea—totalS: o.S.i.as000 seis eeras cise og aion 2 13 49 
COPE POG ai ieeinsieiae «oletsiies a-ieerele aera oc I 5 17 
C@ladGcerac. oo.) 2 te Aviacsa sestcctordeieite - fo) 7 26 
Ostracod ats scanner ch nce aeeen ane I if 3 
Other’ Crustacea’ <..8 sedeckn fekcenutaw ate fo) te) 3 
Miscellaneous—totals....-\csee00-s -siesic noe ve 4 16 | 45 
Insectilarvaee.ostccnsehteee eee eet Neviee I 5 | 6 
@therstormS anes aces ines ee ache 3 II 39 
iota lPNonopeciesierescinsnmecnmece neta | 60 170 429 
method and season of collection. The meager representation 
of the Ciliata may be due to the absence of sewage contamina- 
tion and hence of excessive bacterial development in the creek 
waters. The food supply of many species is thus lacking. The 
absence of a well-developed phytoplankton, aside from dia- 
toms, and the fact that much of the vegetable debris of the 
silt is only in the early stages of decay may account for the 
small number of species of Rotifera and Hntomostraca, groups 
which in part depend upon these sources of food either directly 
or indirectly. The recent origin of the creek water from rain, 
or springs and ground seepage, affords insufficient time for the 
breeding, not only of these organisms which form the more dis- 
tant links in the chain of food relations, but also for many of 
the nearer ones, such as the alge, which subsequently do ap- 
