264 PROFESSOR MARSHALL AND EDWARD J. BLES. 



DESCRIPTION OF THE FIGURES ON PLATES XIII., 

 XIV., and XV. 



Illustrating Professor Marshall and Mr. Bles' Paper on " The 

 Development of the Blood Vessels in the Frog." 



All the figures are from tadpoles of Rana temporaria. 



Figs. 1, 2, and 3 are drawn from individual sections. All the 

 remaining figures are diagrammatical, each being compounded from 

 several sections. Parts are thus shown that really lie at very 

 different levels, but in all cases the shapes and positions of the 

 several organs are inserted from separate camera drawings of actual 

 sections, and are represented as correctly as possible. Organs which 

 are not immediately concerned with the blood vessels are in many 

 cases omitted entirely. 



In the majority of the figures the epiblast is represented black, and 

 its division into sensory and nervous layers is not indicated. The 

 efferent vessels of the visceral arches and the dorsal aorta are coloured 

 red. 



All the figures, with the exception of Fig. 15, are enlarged to the 

 same extent, being magnified 45 diameters. 



In all the figures showing the blood vessels from one side the brain 

 and notochord are drawn from the median sagittal section of the 

 series. 



The small outline figures show the shapes of the tadpoles at the 

 various stages, each of these figures being three times the natural 

 size. 



Alphabetical List of Reference Letters for all the Figures. 



A Dorsal aorta 



A B Basilar artery 



A C Internal carotid artery 



A E Connection between the third 

 branchial afferent and efferent 

 vessels at base of gill 



A F. 1 Afferent vessel of first bran- 

 chial arch : cardiac part 



A F' Afferent vessel of first bran- 

 chial arch : lacunar part 



A F. 2 Afferent vessel of second bran- 

 chial arch : cardiac part 



A F" Afferent vessel of second bran- 

 chial arch : lacunar part 



AF.3 Afferent vessel of third bran- 

 chial arch : cardiac part 



