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ALEXANDER PETRUNKEVTTCH 



Text figure A. Centrurus insulanus, late embryo. Sagittal section in the 

 plane of symmetrj', showing all organs developed at that age. The black spot 

 above is one of the median eyes. In front of the eye is the dorsal dilator of the 

 pharynx. Abdominal tergites marked with Roman numerals I to XII without 

 reference to their embry ©logical history. 1, the first abdominal neuromere; 

 12, the last neuromere; Chj), basal plate of comb; GO, genital opening; PG, poison 

 gland; SG, sting; ST, sternum; the dotted lines showing its antericjr and posterior 

 margins; UP, upper lip (rostrum). Further explanation in the text. 



