FIG. 12. DIAGRAM ILLUSTRATING THEORIES OF PROTOPLASMIC STRUCTURE. 



1, alveolar structure; granules occur only at the angles formed by the alveoli. 2, 

 filar structure, showing filar and interfilar substance. The centrosome (a diplosome) 

 is represented in this portion; it is surrounded by a clear attraction sphere. 3, 

 granular structure; coarse microsomes irregularly disposed. This portion contains 

 three foreign bodies which have been included by the cell, a streptococcus, a crys- 

 tal, and a spheroidal pigment mass. 4> the alveolar walls are formed by regularly 

 arranged microsomes; a vacuole is shown in this section. 5, reticular structure. 



The cell is inclosed by a cell membrane, and contains a central nucleus in which are 

 shown the nuclear membrane, indistinct linin fibrils, deeply stained chromatin in 

 coarse threads and irregular masses (karyosomes), and a centrally situated nucleolus 

 or plasmosome. 



.>; Vv., 

 |S|t5*w II' !*' ' *V 



iillMf l|p 



-'?SX 



FIG. 13. EGG OF THE BLOOD STARFISH IN LATER GROWTH PERIOD. 

 Showing a stage in the change of an earlier granular to a later alveolar condition 

 of the cytoplasm. The nucleus contains many spherical nucleoli of various sizes. 

 The space (a) is a fixation artifact. X 1500. 



11 



