Fig. I. Portion of Esperella mesoderm, showing two gemmules, g and g\ each 

 surrounded by follicle of flattened cells. ^ is a very young gemmule; g\ considerably 

 older: c. :c.= canal wall; /. r.= flagellated chamber. 



Fig. 3. Longitudinal section through the swimming larva of Esperella. The 

 nuclei of the columnar ectoderm cells form a conspicuous zone. In the outer ends of 

 these cells is orange pigment. The inner mass of cells iparenchyme). in the region of 

 non-ciliated pole, differs from the parenchyme in the rest of the body. 



FIGURES IIXrSTRATlXG • NOTES OX DEVELOPMENT OF SPOX(iES. 



