JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATE VII, 



Illustrating Professor Wyville Thomson's paper on the 

 Embryology of Asteracanthion violaceus. 



Fig. 

 1. — Embryo about four hours after complete segmentatiou. 



2. — Embryo four hours later. 



3. — Embryo about nine hours later. 



■i. — Embryo twenty-four hours old. 



5. — Embryo and appendages thirty-six' hours after complete segmentation. 



6. — Peduncle and appendages, which have separated by a natural process of 

 fission from an embryo about a week old. 



7. — Embryo and fully developed peduncular appendage about eight days 

 after segmentation of the yelk. 



8. — Embryo five weeks after complete segaientation, showing the remains 

 of the peduncle, much atrophied, hanging attached to the ambulacral 

 vascular ring. 



9. — Upper surface of embryo about twelve days after segmentation, showing 

 the arrangement of the superficial calcareous plates, &c. 



10. — Lower surface, showing the arrangement of the ambulacral plates. 



