398 



Transactions. 



quadrants in both epibasal and hypobasal regions has proceeded. Those 

 illustrated in figs. 54 to 57 of my previous paper correspond fairly closely 

 with this. The first inclined walls in both main regions of the embryo 

 shown longitudinally in figs. 43a to 43e are apparent, but the subsequent 

 segmentation has followed a somewhat unusual course. 



Figs. 40a-40g.- — Young embryo in oblique transverse section from below upwards at 

 a similar stage of development to those shown in figs. 38 and 39. X 100. 



Figs. 41a— 41g. — Young embryo in oblique transverse section, illustrating absence of 

 octant walls, x 100. 



Figs. 42a, 42b.- — -Young embryo in longitudinal section, showing first segmentations of 

 the epibasal and hypobasal quadrants. X 100. 



Abnormally segmented embryos are set forth in figs. 44a to 44c, 45a 

 to 45p, and 46a to 46d, In each of these the basal wall is clearly to be 

 distinguished, and also the first inclined wall in the hypobasal half, but 

 in the two last-mentioned embryos the segmentation in the epibasal half is 

 rather difficult to interpret. In that shown in figs. 44a to 44d a single 



