PLATE X.— VOLVOX MINOR. 



(From Dodel-Port, after Dr Kirchner.) 



Volvox minor produces both male and female cells in the same colony, but they are ready at different times — the female first, the 

 male afterwards. The germinating Oospore is shown in this Plate, and it is only within the last few years that the process has been 

 traced. The preliminary act in this life drama is shown in the blending of the Antherozoids with the Oosphere. This sets agoing 

 that activity in the cell which finally issues in the formation of a young Volvox-sphere. 



Figures X 880. 



Fig. 1. Oosphere and Antherozoids in contact 



The floating Antherozoids find their way to an Oosphere, and readily blend with it This is the process of 



Fertilisation — and the result is an Oospore. 

 Fig. 2. Ripe Oospore invested by two coats — an outer (Exosporium) and an inner (Endosporium). The investment is unlike that 



of V. globator in being smooth. 



Fig. 3. Exosporium ruptured. 



The swelling contents cause the rupture of the outer coat, and the Oospore is now free to undergo division. 



Fig. 4. First division into two. 



Fig. 5. Division at right angles to the first, forming four daughter-cells. 



Fig. 6. After division into eight comes division into sixteen. 



The Exosporium in this instance has remained attached. 



Fig. 7. Young Volvox formed, green and motile, after about nine divisions altogether in geometrical progression. 



Life History of Volvox. — Volvox multiplies non-sexually, a single cell repeatedly dividing and producing a new colony, or there 

 is sexual reproduction by Antheridia and Oogonia. The Antheridia or male cells are larger than the vegetative cells, 

 and their contents break up into Antherozoids. The Oogonia or female cells are at first flask-shaped, but latterly 

 become spherical, each containing a rounded mass of protoplasm — the Oosphere. The Antherozoids floating in the 

 water ultimately come into contact with a liberated Oogonium, bore through its gelatinous wall, and being merely 

 protoplasm destitute of any investment, they blend with the Oosphere, and so produce a body ready to germinate, now 

 called the Oospore. The future history of the Oospore is indicated in this Plate, where it is seen by repeated 

 divisions to form a young Volvox 



