

153 
noted, but they are rare. The greatest proportion of egg-bearing 
females appears during the rise of the pulse, as 1s seen 1n the follow- 
ing table, which gives the data of the vernal pulse in 1898. From 
ANUR#ZA COCHLEARIS. 







| No. of | | Ratio of 
Date | ovigerous Total Total | eggs to No. of 
females females eggs | individuals dead 
oe lee ea | 800 DRGs We SO0s|< fF 2075 0 
\jostill WO ite eae eae ea | 6,400 15,200 8 800 | Bale 7h} 400 
PNG OTRO} sone) os even ew aaces | 45 ,000 137,800 65,000 | 1 Be 3,200 
25S ee | 536,000 1,022,400 | 552,200 | 1 £185 | 9,600 
JIL 597-1 OS rae eae | 489 , 600 1,145,600 | 643,200 | if S eei(htes | 99 , 200 
UES? Ih AgeS ea eee | 110,400 434,800 | 160,000 | Lest 2ia7 ty 2 100, 008, 
WWeimeP eb teste ats zoe cet | 6,000 21200 | LOO | es 2 OAS 1,800 
IMIG? Sh Shee see teee ee eee 3,000 11,200 S4OOR is Se 29 | 1,800 

April 12 to the crest of the pulse on May 10 (not inclusive) the aver- 
age ratio of eggs to individuals was 1 to 1.87. From the.crest to the 
foot of the decline inclusive the ratio is 1 to 2.98. The number of 
empty loricie is given below, and it will be noted that on the week 
prior to the crest of the pulse there were 107 living to one dead;on 
the crest itself, one to twelve; while the week following the crest of 
the pulse there was an empty lorica for every 4.3 living females. 
Rapid multiplication thus attends the rise of the pulse and rapid 
destruction its decline. Parasites were very rarely observed in this 
species. The decline of a pulse is thus due to the cessation of 
reproduction and a relatively heavy death rate. 
Apstein ('96) finds that in Lake Plon Anure@a reaches its maxi- 
mum in July and is at its minimum in April. It is everywhere 
common in the German waters. A. tecta, on the other hand, was 
found only in the smaller lakes and in great numbers, replacing 
cochlearts in warmer months to some extent. Lauterborn (98) 
regards it as the most abundant rotiferin the Rhine. Our statistical 
records do not show that this is the case in the Illinois, for it is here 
