78 



THE LARVA OF THE BLOW- FLY. 



reference to Fig. 14, 2, which represents a transverse section 

 through the region indicated by the line 2 in Fig. 13 : cp is the 

 cephalo-pharyngcal band ; s/), the suspensory membrane, and a, 

 the base of the antennal rudiment. 



There is a large blood sinus between them, in which the 

 oesophagus lies, into which the dorsal vessel opens through the 

 ring. The suspensory membrane, up, forms its roof, and the 



KiG. 13.- A semi-diagramimtic reprcstimiiDn of the Head Discs and Ilemispheies 

 seen from above : / 2 -ind j, pi incs of the sections / 2 and 3 in Fig. 14 ; 

 mx, maxillary disc ; //;, phiryngeal , a, antennal ; 0, optic discs ; pf, prefacial 

 rudiment ; cp, cephalo-pharyngeal band ; cr, crop; <://, cerebral hemisphere; ft, 

 retina ; s, optic stalk ; / s, provisional sac. 



discs its lateral walls. The inner and posterior part of the wall 

 of the disc sac is occupied by the epiblast of the disc ; its outer 

 wall is the provisional membrane. 



The Ring was first described by Weismann as follows [2, 

 p. 125] : ' The anterior part of the dorsal vessel lies above the 



