MICROSCOPIC FORMS OF VEGETABLE LIFE. 



239 



DEVELOPMENT OF VOLVOX GLOBATOR (after Williamson/. 



Fig. 1. Young Volvox ; a, primordial cell of secondary sphere ; 6, polygonal masses of endo- 

 chrome, separated by hj*aline substance. 



2. The same more advanced ; a, a, polygonal masses of endochrome ; 6, 6, their connecting pro- 

 cesses ; c, primordial cell of secondary sphere. 



3. The same mora advanced, showing an increase in the size of the connecting processes, a, a, 

 and duplicative subdivision of the primordial cell. 



4. The same more advanced, showing the masses of endochrome more widely separated by the 

 interposition of hyaline substance, and each furnished with a pair of flagella; whilst the primordial 

 cell,/, has undergone a second segmentation. 



5. Portion of the spherical wall of a mature Volvox, showing the wide separation of the endo- 

 chrome-masses still connected by the processes 6, b ; the lines of areolation, c, dividing the hyaline 

 substance ; and the long flagella, e. 



6. 7, 8. Secondary sphere, or macro-gonidium, developed by the progressive segmentation of the 

 primordial cell. 



9. Single cell from the wall of a mature Volvox, showing the endpchrome mass, 6, to contain 

 two vacuoles a, a, and to be surrounded by a hyaline envelope, d, having polygonal borders. 



10. Portion of the wall of a young Volvox, seen edgeways, showing that its sphere is still invested 

 by the hyaline envelope of the original cell, which the flagella penetrate but do not pierce. 



11. Two cells from a mature Volvox, seen edgeways, showing the inclosure of the endochrome-' 

 masses in their own hyaline investment, and the persistence of the general investment (pierced by 

 the flagella) around the entire sphere. 



