276 CHAS. W. PIAEGITT, The eiirly development of Eudeudrium. 



A. portion of section, showing a nest of nuclei with in a 

 a single nucleus fully organized, from same section. About 



Two nuclei a and />, in amitotic division. 



Cell in mitotic division. 



Several cells from same section in mitotic division. 



Plate 16. 



I'ig. 20. Section of an eggs showing fully developed ectoderm at 

 Ect and only partially developed at opposite pole. Glandular cells at G. c. 

 No signs as yet of entoderm-formation. 300 : 1. 



Fig. 27. Portion of ectoderm more highly magnified and showing 

 cytologic character of the gland-cells G.c^ lower with apparently two 

 nuclei. 



Fig. 28. Portion of section showing aspects of the embryonic de- 

 velopment shortly before the escape of the planula. The vacuolated 

 condition of the ectoderm at this time is very conspicuous. 



Fig. 29. Two of ectodermal gland cells highly magnified. 



Fig. 30. Aspects of ectoderm at about time of escape of the 

 planula. 



