Ixxxviii THE BEGINNINGS OF LIFE. 



have derived their origin from any similar or dissimilar 

 existences outside the Volvox, nor could have themselves 

 entered within the sphere by solution, became very evident 

 from observing the different stages by which the ordinary 

 zoospore gradually arrived to the condition now under dis- 

 cussion' After the altered amoeboid zoospore had begun 

 to travel, 'it was always noticed that for every one such 

 moving body in the Volvox there was the empty space of a 

 missing zoospore.' A similar amoeboid change may also 

 overtake such zoospores as have gone on to the first stages 

 of gemmule growth. 



In other cases a very interesting deviation from the 

 ordinary gemmule growth occurs, which has also been 

 described by Dr. Braxton Hicks. As a rule the zoospore 

 divides so as to lead to the formation of about thirty- six 

 cells within the common cell-wall. ' These/ Dr. Hicks says, 

 'in the ordinary way would pass on to further sub- division, 

 producing almost from this point ciliated cells, which, again 

 re-dividing, would produce the ultimate zoospores held to- 

 gether by the hollow, spherical membrane or, in other 

 terms, the ordinary Volvox. Instead, then, of the sub-division 

 forming the ciliated cells, which tend towards the exterior of 

 the mass, motionless spores or gonidia are produced, which 

 do not tend outwardly, but which retain their position, 

 except that they become more separated from each other by 

 the increase of the intervening mucus. Watching these 

 throughout the period above mentioned, I found that the seg- 

 mentation continued in various modes till the masses became 

 one-eighth of an inch in diameter, preserving more or less of 

 a globular form, but indefinite so far as any investing mem- 

 brane was concerned. ... At first the division went upon 

 the binary plan 1 ; after which some of them divided into 



1 Dr. Hicks has represented these various changes on PI. IX. of 

 'Journ. of Microsc. Science,' 1861. 



