Gall-producing Anguillulide. 347 
and pushing about; and on the other, when dead, although 
they may lie straight, they may always be unduly extended 
er contracted, which with such small individuals may easily 
cause a difference of 0:1 millim. or even more. ‘The young 
Anguillule not yet sexually mature, which always occur asso- 
ciated with the fully developed and sexually mature individuals, 
and indeed in greater number than the latter, are of very dif- 
ferent lengths according to the degree of their development. 
In the form of the body they resemble the sexually mature 
individuals; only the granules and vesicles of the contents of 
the body are larger. 
The egg is about twice as long as broad, equally rounded 
at the two ends ; its contents are finely granular, with several 
vesicles scattered through them. Some time before hatching, 
the young Anguillule may be seen through the delicate mem- 
brane of the egg. ‘They lie elliptically curled up in the egg, 
following the form of the latter. When hatched they are about 
five times as long as the egg, or about one fifth of the length 
of the adult*. ‘The circumstance that we almost always find 
together all the stages of development of the Anguillula of 
the milfoil, from the egg to the egg-laying individual, may 
be explained by supposing either that in this species several 
generations follow one another during the favourable season of 
the year, or that the oviposition takes place at very various 
times, as, indeed, Dr. Kiihn supposes to be the case with 
Anguillula dipsact. 
The mode of life of the milfoil-Anguillula probably re- 
sembles exactly that of A. dipsaci, Kiihn, A. tritic?, Roff., 
and other Anguillule of plants. The young asexual Anguil- 
lulee winter in the leaf-galls ; or the last-deposited eggs may 
winter outside the galls; and in the spring, when the galls are 
already rotted by the moisture of the soil, they quit them, 
creep upon the young shoots of the milfoil, bore into the still 
tender tissues of the expanding leaves, and produce upon them 
afresh the galls described at the commencement of this paper, 
in which they become further developed, and give birth to 
new generations. ‘Towards autumn the original abundance of 
sap in the galls is gradually exhausted, their green colour 
passes to yellow; finally they become withered and wrinkled ; 
and the individuals contained in them, which have never 
quitted the gall, stiffen or become dried up at the beginning of 
the cold season, to be awakened again from this apparent 
death only by the sunshine of spring. 
* In the viviparous Anguillulidee, such as Anguillula aceti, glutints, 
fluviatilis, &e., the young are born still enclosed in the egg-membranes. 
