268 Transactions.—Zoology. 
the mackerel gull (Larus scopulinus) and the curlew (Limosa baueri). But if 
Hoffmeister's statement is correct—which is very probable—that the Sco- 
lopendra are their bitterest enemies, this instinct must subserve some 
other purpose as well, as they almost invariably open their burrows at 
night. As earth-worms habitually lie close to the mouths of their burrows, 
the stopping may not only tend to give them a sense of safety, but exclude 
the light. 
In loose ground worms rarely void their castings on the surface, using 
old burrows and cavities. Henson’s statement that worms habitually use 
old burrows—in solid ground—for this purpose, is doubted by Darwin; if 
he meant that the filling-up of the burrows was entirely due to this cause, 
he is probably in error, for it is evident, in some soils, that heavy rain 
` causes the walls of the burrows to flow and slide inwards ; portions of the 
sub-soil then collapse, forming alternate streaks of black and light soil. 
(Mr. Darwin points out that when the soil is not viscous enough to flow 
inwards, the same end is attained by another agency.) At the same time 
my own observations lead me to agree with Henson as to the habitual use 
of the old burrows for the purpose of voiding castings in. During the 
winter months and wet weather fresh castings retaining their convolutions 
are to be met with at various depths in the solid ground, and in positions 
which preclude the idea of their having been washed down; and it appears 
to me that the amount of black humus used in lining the walls, is inade- 
quate to fill up the burrows and chambers to the extent they often are. 
Again, fresh castings are to be found in the holes left by decayed roots, and 
sun-cracks. These holes are generally filled up with fine black earth, most 
of which is apparently worm-castings. Owing to the nature of the sub-soil, 
in which my researches have been chiefiy carried out, portions of the bur- 
rows, and especially the chambers, often retain their form for many months 
without being filled up with humus. This of course is favourable for 
observations. 
Want of leisure time has prevented my systematically collecting worm- 
castings off a measured piece of ground, so as to form an estimate of the 
amount of earth annually thrown out on an acre of land, fairly stocked 
with worms; but Darwin who has carefully gone into the matter says :— 
“In many parts of England a weight of more than ten tons of dry earth 
annually passes through their bodies and is brought to the surface on each 
acre of land.” Compared with the European, worm-castings in New Zea- 
land are light, the larger castings, fresh and well-dried, weigh about ‘8 
of an ounce ; the smaller and most numerous weighing only ‘07. Although 
the worm-castings are light, the amount of earth ejected in favourable 
ground in the course of years is considerable, apparently equal to some 
