492 Observations on the Development of Ox JVarhle, 
tremity of processes somewhat bent apart at the ends by which 
they are attached to the crescents, and attached by the other 
ends to the membranes or tissues forming the gullet, or internal 
sac of the maggot ; see Fig. 4, showing, at 1 and 3, the crescent- 
shaped forks in slightly different positions, and at 2, the appa- 
ratus viewed sideways, so as to show the curved ends of the 
processes. The material is chitinous or horny, and the colour 
yellowish-brown, and, though excessively minute, the hook forms 
a very serviceable cutting or dragging implement. 
The possession of this apparatus by the maggot in this early 
stage is a great confirmation of the belief that the creature gets 
down to the sub-cutaneous tissues of the hide simply by cutting 
its way forward. We appear here to have both cause and effect, 
for we find as a regular thing that there is a minute track down 
to the embryo warble beneath the hide, which said track has the 
appearance of having been cut or gnawed ; and in the exceed- 
ingly young and still worm-shaped maggot found on Jan. 27, 
there was the apparatus for cutting, or gnawing. 
The duration of special habits of life in the maggot may be 
divided into three periods : that above mentioned, when its 
chief work appears to be making its way down ; the next, when 
it starts into the active state which precedes its first obvious ap- 
pearance in the opening warble, and in which its most important 
work is forcing its way up again, tail foremost ; and the third, 
in which, having formed the opening, it lies within, feeding, 
mouth-end downwards, in the filthy discharge its own presence 
causes, until it is ready to leave the hide, and turn to the chrysalis 
state. 
The method by which the perforation is effected has given 
rise to much ingenious speculation ; but, by carefully watching 
the habits of the young living maggots, and likewise the con- 
dition of the perforation in fresh hide during the very short 
time which is occupied by the first formation of the perforated 
swelling known as the warble, the whole process appears clearly 
traceable. 
The tip of the tail of the maggot, which is of necessity the 
point of the wedge that precedes its owner up the hide, is not 
now ended, as in its latest state, by two flat, kidney-shaped 
spiracles (Fig. 5) ; whilst the boring work has to be done, the 
spiracles are of a different form. They are, during this time, 
somewhat club-shaped, or, when highly magnified, appear like 
short bent cylinders (Fig. 8, p. 495). These are of horny or 
chitinous mateiials, and each of the pair of spiracles, or 
breathing-pores, is placed at the extremity of a large trachea or 
breathing-tube, which pair of tracheae are tied together by a 
transverse tube placed near the spiracles. The maggot is thus 
