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On the Structure of the Head of the Blowfly Larva, 

 and its Relations to that of the Perfect Insect. 



By B. Thompson Lowne, F.R.O.S.Eng., F.L.S., &c, Professor 

 of Biology at the Royal Veterinary College, &c, &c. 



(Bead June 24th, 1887.) 



The larva of the blowfly is frequently described as acephalic or 

 headless ; more correctly it is without any chitinised cephalic 

 shield (Kieferkapsel), for a head is certainly present although in 

 many respects it is rudimentary. 



In the egg, twelve hours after impregnation, the embryo 

 possesses a head ; in most respects similar to that of an embryo in 

 which a chitinised head capsule is subsequently developed in the 

 larva. At this period the head consists of the cephalic fold or 

 forehead (Vorderkopf), a prolongation of the ventral formative 

 band (Kevmvulst) over the anterior pole of the yelk. The cephalic 

 fold is separated from the ventral formative band by a depression 

 or pit, the future stomodasum or involution from which the anterior 

 part of the alimentary canal is developed. On either side of the 

 cephalic fold a lobe-like plate is developed, connected with the 

 ventral formative band by a narrow stalk. These are the pro- 

 cephalic lobes of Huxley, and form the lateral and posterior 

 regions of the head. The antennas are usually developed from bud- 

 like projections of the procephalic lobes, but in flies the develop- 

 ment of the antennas takes place at a much later period, after the 

 escape of the larva from the egg. 



Behind the pouch from which the stomodasum is developed the 

 ventral formative band undergoes segmentation. At first three 

 segments are formed in the region of the future mouth, the 

 thoracic and ventral segments being formed at a slightly later 

 period. A bud-like projection then appears on each side of each 

 of the three first-formed segments ; the rudimentary mandibles 

 and first and second maxillae. Subsequently similar buds appear 

 for the development of the thoracic limbs in those insects in which 

 such appendages exist in the larva. In the fly, however, no 



