EXPLANATION OF PLATES VIII, IX, AND X, 



Illustrating Mr. F. M. Balfour's Notes ou the Develop- 

 ment of the Araneina. 



PLATE Vm. 



Complete List of Reference Letters. 



ch. g. Ganglion of chelicerse. c. I. Caudal lobe. cTi. Chelicerge. pd. 

 Pedipalpi. pr. I. Prasoral lobe. pp^. pp^. etc. Provisional appendages. 

 p. c. Primitive cumulus, sp. Spinnerets, st. Stomodseum. 



I — IV. Ambulatory appendages. 1 — 6. Postoral segments. 



Fig. 1. — Ovum, with primitive cumulus and streak proceeding from it* 



!FiG. 2. — Somewhat later stage, in which the primitive cumulus is still 

 visible. Some distance from it is a white area, which is probably the 

 rudiment of the procephalic lobe. 



Fig. 3a and 3*5. — View of an embryo from the ventral surface and from 

 the side when six segments have become established. 



Fig. 4. — Yiew of an embryo, ideally unrolled, when the first rudi- 

 ments of the appendages become visible. 



Fig. 5. — Embryo ideally unrolled at the stage when all the appendages 

 have become established. 



Fig. 6. — Somewhat older stage, when the limbs begin to be jointed. 

 Viewed from the side. 



Fig. 7. — Later stage, viewed from the side." 



Fig. Ta. — Same embryo as fig. 7, ideally unrolled. 



Fig. 8a and 8<5. — View of an embryo from the ventral surface and 

 from the side, after the ventral flexure has considerably advanced. 



Fig. 9. — Somewhat older embryo, viewed from the ventral surface. 



PLATES IX AND X. 

 Complete List of Reference Letters. 



ao. Aorta. atS. ^. Abdominal nerve cord. c/i. Chelicerae. ch. g. Gan- 

 glion of chelicerffi. ep. Epiblast. ht. Heart, hs. Hemispherical lobe 

 of supra-oesophageal ganglion. /. I. Lower lip. m. Muscles, me. Meso- 

 blast. mes. Mesenteron. mp.g. Malpighian tube. ms. Mesoblastic 

 somite, ce. CEsophagus. p. c. Pericardium, pr. Proctodeeum (rectum). 

 pd. Pedipalpi. pd. g. Ganglion of pedipalpi. pr. c. Primitive cumulus. 

 *. Septum in abdomen, so. Somatopleure. sp. Splauchnopleure. st. 

 Stomoda:um, su. Suctorial apparatus, su. g. Supra-oesophageal ganglion. 

 th. g. Thoracic ganglion, v. g. A'entral nerve cord. yk. Yolk. y. c. 

 Cells derived from yolk. i/. n. Nuclei of yolk cells. 



\g — IV ^. Ganglia of ambulatory limbs, 1 — 16. Postoral segments. 



