SEXUAL GENERATION OF VOLVOX. 257 



has commenced. What is the subsequent destination of these Amoe- 

 boid bodies, has not yet been certainly ascertained ; but from his 

 observations upon similar bodies developed from the protoplasmic 

 contents of the roots of Mosses, Dr. Hicks thinks it probable that 

 they become converted into minute ciliated bodies, which he has 

 found to occur in larger or smaller groups, enclosed in cavities 

 formed in the mucous layer just underneath the transparent sphere : 

 of the subsequent history of these, however, we are at present left 

 entirely in the dark.* 



199. But the reproduction of Volvox is not effected only by 

 processes which consist, under one form or another, in the multi- 

 plication of cells by subdivision. As already pointed out, the Life 

 History of no organism can be considered as complete unless it 

 includes an act of Conjugation, or some other form of the true 

 Generative process ; and the observations of Dr. Cohn f fully bear 

 out this proposition in regard to Volvox. A sexual distinction 

 between Sperm-cells and Germ-cells, such as is seen in Vau- 

 cheria (§ 245), shows itself in certain spheres of Volvox; these 

 being distinguishable by their greater size, and by the larger 

 number of their component utricles. They are generally monoecious, 

 that is, each sphere contains both kinds of sexual cells ; the greater 

 number of cells, however, remain neutral or asexual. The female 

 or Germ-cells exceed their neighbours in size, acquire a deeper 

 green tint, and become elongated towards the centre of the sphere ; 

 their endochrome undergoes no division. In the male or Sperm 

 cells, on the other hand, though resembling the germ-cells in size 

 and form, the endochrome breaks-up symmetrically into a multi- 

 tude of linear corpuscles, aggregated into discoidal bundles. These 

 bundles are beset with vibratile cilia, and move-about within their 

 cells, slowly at first, afterwards more rapidly, and soon become 

 separated into their constituent corpuscles. Each of these has a 



* The known care and accuracy of Dr. Hicks give a weight to his 

 statements as to the Amoeboid condition sometimes assumed by the con- 

 tents of Vegetable cells, which justifies their provisional reception, not- 

 withstanding their apparent improbability. It will be seen as we proceed 

 (§ 269) that the phenomenon is not so exceptional as it at first sight 

 appears ; and it does not involve any real confusion between the boun- 

 daries of Animal and Vegetable life. For the mere fact of spontaneous 

 motion by the extension and retraction of processes of an indefinite 

 Protoplasmic mass, no more makes that mass an Animal, than the 

 vibration of the Cilia formerly supposed to be exclusively possessed by 

 Animalcules alters the truly Vegetable character of the zoospores of a 

 Conferva or of the Tourer-sphere itself. No proof has yet been given 

 that these Vegetable Amoeboids take into their interior, and appro- 

 priate by an act of digestion, nutrient materials supplied either by the 

 Vegetable or by the Animal kingdom ; so that, if the doctrine already 

 stated (§180) as to essential distinction between the two Kingdoms in 

 this particular be correct, such bodies remain as much on the Vegetable 

 side of the line of division as if they had been entirely motionless. 



t "Annales des Sciences Naturelles," 4ieme Ser., Botan., Tom. v. 

 p. 323. 



