THE EMBRYOLOGY OF A TERMITE. 567 



EXPLANATION OF PLATE XXXIL 



The outlines of the figures on this plate were drawn with the aid of a camera. 

 They are magnified 55 diameters by Bausch & Lomb's oc. 50 mm., object. 17 mm. 



The series represents, diagrammatically, in side view and partly in optical 

 section, the principal stages in the development of the Termite embryo, from the 

 complete establishment of the germ-disc to the dorsal closure of the body-walls. 



The origin and history of the embryonic membranes are particularly emphasized. 

 The general relations of the embryo to these membranes, to the yolk-mass, and 

 to the axes of symmetry of the egg are also well brought out. Note the position 

 of the micropyles, on the primary (and definitive) ventral surface of the posterior 

 end of the egg, in studying the remarkable changes in position which the embryo 

 passes through. 



Stage A. Germ-disc when first established, em. ; extra-embryonal blastoderm, 

 ex. ; yolk, y. ; chorion, ch. ; micropyles, my. 



" B. Germ-disc with posterior amniotic thickening, am.t., and mesodermal 

 plug. 



" C. Amnioticfold. Amnion apart of disc, aw. ; serosa, extra-embryonic, i'. 



" D. Amniotic fold just before closure of amniotic cavity. Amniotic cavity 

 open anteriorly, amc. ; serosa, s. 



" E. Immediately after closure of amniotic cavity, amc. 



" F. Early stage in the posterior elongation. The amnion begins to be 

 stretched. 



" G. Elongating germ-band before appearance of cephalic lobes. Amnion 

 not fully stretched posteriorly. Mesoderm a flat under-layer. 



" H. Unsegmented germ-band with cephalic lobes, cp.l. 



" I. First appearance of segments. Antennae, ant. ; mandibular segment, 

 md.; first maxillary, waj;.'; second maxillary, wax.^ : first thoracic, 

 th.^\ tail-piece, ta. 



" K. Further elongation. Addition of second and third thoracic segments, 

 th.^ and th.^ ; and an indistinct first abdominal, ab.^, from anterior 

 portion of tail-piece. Appearance of labrum, /., and stomodeum, 

 St. Folding of head up from yolk. 



" L. First stage of caudal flexure. Cephalic and thoracic appendages well 

 marked. 



" M. Caudal flexure pronounced. Abdominal segments established. Proc- 

 todeum, pr., well developed. Anterior appendages prominent. 



" N. Just before " revolution." Head globular and standing off from yolk. 

 Maxillae tri-lobed. Anterior appendages long and beginning to 

 segment. Abdominal appendages prominent. Stomodeum and 

 proctodeum long. 



" 0. " Revolution." Head slipping up along ventral surface to the anterior 

 pole of the egg. Embryonic membranes, especially serosa, contract- 

 ing dorsally. Proctodeum, pr., a long tube. Second maxillae 

 moved inward and not seen. 



