A QUEER HOUSE BUILDER 107 
guest gall-fly comes along and lays her egg side 
by side with the true gall, and the two babies are 
reared in one cradle; again a parasitic gall-fly 
deposits a companion egg and the little parasite 
when it hatches proceeds to feed upon the true gal] 
baby. Another point, the individual hatched may 
be a sure enough gall-fly, but instead of looking 
like its parent, it resembles its grandparent, which 
was another creature altogether. The subject of 
gall-fly generations is like a Chinese puzzle. One 
may have wings, another be wingless; one may be 
all females, another of both males and females; 
we see their case paralleled in the undersea world 
by the hydroids and jellyfishes. 
“ Strangely enough, or perhaps, knowing 
Mother Nature, we had better say as is to be ex¬ 
pected, the little gall nurseries all have their pro¬ 
tective features. Some galls exude sweet juices 
and thus attract the honey-making ants who at 
once establish a guard about it, and thenceforth 
protect the rich stores with their lives if need be. 
Other galls are covered with sticky hairs which 
entrap would-be marauders. Again the spongy 
growth is too thick to be readily broken, or the 
hollow chamber is so large that a groping tongue 
cannot readily discover the small occupant. Or 
perchance, as in the oak apple here, the baby is 
further safeguarded by being hidden away in a 
wooden cradle; some galls even have hard stony 
