1951] 
Humes and Russell — - Najadicola ingens 
119 
the gravid period, when unparasitized gills without mites 
or papillae were completely gravid. 
3. Living egg masses of N. ingens were found in A. 
cataracta only in June, July, and August, months which 
coincided with the highest water temperature. June egg 
masses were recently laid, July masses were older for the 
most part, and August masses were mostly near hatching 
or had already hatched. This indicated a rather sudden 
oviposition early in June, followed by a slackening of egg 
laying until September, when it ceased. Egg masses which 
have not hatched by September probably die and may re- 
main in the suprabranchial chambers for several months. 
4. Dead adult males were found in A. cataracta through- 
out the 13 months in about equal numbers. Dead adult fe- 
males were most abundant in July, one month after the 
maximum oviposition, suggesting that at least some females 
die after oviposition and that their bodies may remain in 
the suprabranchial chambers for several months. 
5. Nymphs were found in small numbers in A. cataracta 
in all but 4 months (December, January, May, and Sep- 
tember) without significant seasonal variation. 
6. An average number of 1.58 adult mites per parasitized 
clam was recovered from A. cataracta. This average 
number and the relative numbers of male and female mites 
showed no seasonal trends. The sex ratio of males to 
females was 1.76:1. 
7. Throughout the 13 months the mites most often oc- 
curred in the outer suprabranchial chambers of A. cata- 
racta. In only a few cases were mites found in the inner 
or in both outer and inner suprabranchial chambers. 
