268 Transactions. — Zoology. 



the mackerel gull {Larus scopulinus) and the curlew (Limosa baucri). But if 

 Hoffrneister'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-tip 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 chiefly 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 *3 

 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 



