A YORKSHIRE NATURALIST 117 



time in a solution of iodine and glycerine, and in a 

 few of the organisms thus treated I obtained what I 

 was in search of, and which gave me a clue to the 

 structural history of the Volvox. 



I found that this hexagonal object had originated 

 from one of the numerous minute green points 

 already referred to. It began to enlarge, becoming 

 conspicuous among its smaller neighbours. It next 

 split into two, then into four, until a succession of 

 such binary divisions produced a spherical cluster of 

 green protoplasm enclosed within a delicate trans- 

 parent sphere. At first these subdivided atoms 

 adhered closely one to another ; at length the divi- 

 sions ceased, but the sphere continued to enlarge, 

 became hollow, and eventually the green objects 

 arranged themselves in a single layer surrounding 

 the central cavity, yet adhering to each other by their 

 thin margins. This absolute contact of each proto- 

 plasm with its neighbours became interrupted except 

 at five or six points. As this interrupted continuity 

 increased, each protoplasm ceased to retain its 

 homogeneous condition ; it separated into two ele- 

 ments. The small green mass became suspended in 

 a transparent colourless fluid, the two elements now 

 becoming enclosed within a delicate colourless cell 

 wall. The further enlargement of each of the 

 cells thus produced caused the five or six points of 

 mutual contact to become drawn out into the delicate 

 threads already referred to. The little compound 

 sphere next became detached from the inner surface 



