COMPARATIVE ANATOMY. 



285 



the bottom transformed into a young CJiihm. During the last 

 transformation, two lateral eyes appear on the anterior ventral side 

 of the body. The development of the circulatory system, the 

 nephridia, the genital organs, and the ctenidia has not been fol- 

 lowed. 



Fig. 23. — Diagram of the Organisation of a Pentremites (original). 



We fear our extracts have already been too lengthy. We can- 

 not, however, resist the pleasure of presenting our readers with 

 Fig. 23, which shows the Ambulacral Skeleton of the Echinodermata. 



