IN VEGETABLE BIOLOGY. 377 
vocinee ; but it seems to me better to employ it in the old sense, 
as the name of a suborder including within its limits all motile 
types with external cilia, rather than to restrict it to oogamous 
forms alone. Indeed, it seems possible to classify all the Chloro- 
phycee upon this system: thus, for instance, among the fila- 
mentary forms (Confervoidee) we may distinguish the oogamous 
families Cylindrocapsee, Spheroplee, and (Edogonie@ from the 
isogamous Ulothricacee, Conjugate, and Siphonocladee ; and we 
may separate, among Siphonee, the oogamous Vaucheriec and 
the isogamous Botrydiee. Soo, too, Volvocee (oogamous) and 
Pandorinee (isogamous) will be two families of Volvocinee. This 
classification is more in accordance with phylogeny than is one 
which makes, as it would seem, too great a distinction between 
oogamy and isogamy—important though the differences between 
them are; since in all probability but few botanists would 
maintain all oogamous forms to have descended from one common 
stock, and all isogamous from another. 
Apiocystis is therefore a degenerate type of Volvocinee : origi- 
ginally able to move freely, thanks to its powerful cilia, it has in 
large measure exchanged this way of life for an attached existence. 
The alternative view is that it is an up-grade type, and nota 
down-grade one at all; that we have here the form whence Volvo- 
cine, or at least Pandorine@, have sprung. I venture to think 
this view to be untenable, seeing that the cilia, which in the vast 
majority of cases are not used in propelling either the organism 
as a whole, or considerable parts of it, are developed even toa 
far greater extent than are those of all hitherto described Volvo- 
cinee. Even Lamarckians, with their “ prophetic structures," 
would scarcely dare to class these wonderful cilia among such. 
This point being settled, we are enabled to draw one wide co- 
rollary from it: viz. that in the vegetable as in the animal kingdom 
degeneration is the penalty for abdication of a free existence. 
The Volvocinee would seem to be types of relatively high 
organization, motility giving them great advantages in respect of 
light, temperature, &e. over other alge. How, then, can retro- 
gression be accounted for? It would appear that increase in 
size is to be looked upon as the cause. This increase implying 
multiplication of the gonidia, would of course be favourable to a 
species ; butif carried beyond a certain point, it would be accom- 
panied by the drawback of diminished motility: in fact, with 
every advance in size, the object of motility would tend to be 
