203 
The sense organs of the head have been somewhat altered ; 
the conical optical tubercle is shorter than in the first stage, being 
not longer than broad, and the sense facettes are now situated on 
the flattened top of a little papilla. 
The mouth-hooks have a rather curious shape. They are split 
up into two branches; at the end the dorsal branch is dilatated 
and here provided with a number of spines; the ventral branch is 
somewhat ventrally curved, Between the two branches the inte- 
gument carries some rows of very small spines, whose bases are 
connected. The anterior part of the pharyngeal skeleton is sepa- 
rated from the posterior by an articulation; it consists of two la- 
teral plates, connected by a ventral bar; on the upper side of the 
plates is found a strong tooth; the posterior part of the skeleton 
also consists of two plates, which are broad and deeply incised at 
the end. The anterior spiracles are found intersegmentally be- 
tween the second and third segment; the atrium is long; the end 
is fan-shaped, terminating with five knobs; the atrium of the po- 
sterior spiracles bears three oblong knobs. 
Third stage: The length of the. full-grown larvæ was ca. 
15 mm. The posterior end is obliquely truncate, in the middle 
deeply excavated, carrying the posterior spiracles in the centre of 
the excavation. The sense. organs of the head are similar to those 
of the second stage. On each side of the mouth-opening is found 
a group of some few strong spines "and behind these some rows of 
minute spines. The mouth-hooks articulate posteriorly with the an- 
terior pharyngeal sclerite, which is formed, as in the 2. stage, by 
two lateral plates, each provided with a strong spine on the upper 
side; the plates are connected by a somewhat prominent ventral 
bar; the posterior end of the sclerites articulates with the posterior 
pharyngeal sclerites. 
The anterior border of segments 2—4 is provided with rows 
of spines. "On the ventral side of the segments 5—11 there is a 
Spiniferous pad, behind which occur some smaller transverse pads, 
and on the side of the segments are found some minute warty tu- 
