130 



HEREDITY AND ENVIRONMENT 



Fig. 29. Gastrula and Larva of Styela, showing the cell 

 lineage of various organs, and the distribution of the differ- 

 ent kinds of protoplasm to these organs. Muscle cells are 

 shaded by vertical lines, mesenchyme by horizontal lines, ner- 

 vous system and chorda by stipples. 



