i68 



PATTERNS AND PROBLEMS OF DEVELOPMENT 



externally as well as internally, usually from the basal region (Fig. 57, 

 H, I), occasionally over most of the surface. This emigration occurs 

 more frequently and to a greater extent in LiCl than in other agents used. 

 The cells given off are normal in appearance, with no evidence of cytoly- 



B 



D 



Fig. 57, A-K. — Phialidiiim gregariiini. Normal and differentially inhibited development. 

 A-C, normal development of planula; D, E, differential inhibition in early stage with increase in 

 number of immigrating cells and extension apically of region of immigration; F, G, differen- 

 tially inhibited early planulae, excessive immigration; H, I, immigration and emigration; 

 /, K, obliteration of polarity, equal immigration from all regions resulting in solid spherical 

 mass (from Child, 19256). 



sis; the solid planulae remain alive and, as will appear, may develop fur- 

 ther. With more extreme inhibition in early blastula stages all evidences 

 of polarity are obliterated, immigration occurs equally from all parts of 

 the wall, giving rise to completely solid spherical larvae without visible 

 structural differences of any kind (Fig. 57, J, K). Ciliary co-ordination 



