414 



MARGARET ROBINSON. 



In fig. 54 I have shown seven mesoderm cells {h.c.) lying 

 just under the dorsal thickening of the ectoderm. These 

 I think are probably the first traces of the heart. It is in 

 just this way, according to Nusbaum (1887), that the heart 

 first appears in My sis. 



At the base of the second antenna the rudiment of the 

 antennary gland can be distinctly seen in some specimens 



Proc. 



Mes. 



Ec 



. -£rv. 



DiAGiiAM 3. — Median longitudinal section through embryo at 

 Stage E. Lettering as in Diagram 2. 



(fig. 55). It is, roughly speaking, triangular in shape with a 

 triangular lumen. The cells, of which there are not more 

 than six or seven, have a finely granular protoplasm with 

 here and there a lump or rather globule of something which, 

 since it stains in the same way as the yolk, I take to be the 

 excretion. There are still some vitellophags to be seen. 



Endoderm. — On the dorsal side the endoderm now extends 

 along almost the entire length of the embryo, but ventrally 

 still only a little way in front of the curve formed by the 

 folding over of the papilla (Diagram 3). 



