IN VEGETABLE BIOLOGY. 365 
in the size of the cilia, the largest of which can only be described 
as gigantic; for besides reaching to a distance at least ten 
times as great as the length of the gonidia, their thickness is so 
considerable as to render them easily visible with a 3-inch or even 
a l-inch objective. Each cilium can be traced penetrating the 
common wall by means of its own aperture, to be inserted upon 
the colourless extremity of the gonidium ; in the surrounding 
water the cilia lie straight and perfectly motionless. The sphe- 
roidal, or at most very slightly ovoidal, gonidia have each a con- 
spicuous vacuole which seems to be in a condition of permanent 
diastole, contractility never having been observed in it. Lying 
close to the vacuole, often at its proximal end, is a small nucleus 
visible only after staining ; hematoxylin and acetic-methyl green 
are the best reagents for showing it up, especially the latter, which 
dyes surrounding parts Jess deeply than does hematoxylin. The 
chloroplast also contains several small pyrenoids scattered 
through it. 
The mother-sae grows in all three dimensions of space, so 
that the gonidia are soon clearly seen to be ranged round its 
wall, its interior being filled with water. Meanwhile gonidial 
division is proceeding apace, though not necessarily at the same 
rate in all cases; for larger undivided gonidia may frequently be 
seen lying beside the smaller products of segmentation: this 
accounts for the rarity of arithmetical exactitude where the 
number of gonidia exeeeds eight and sometimes even a lesser 
number ; it will be remembered that Naegeli mentions thirty- 
two as the limit below which there is no irregularity. In 
many cases division of the gonidium is preceded by secretion of a 
firm wall round it (Pl. LV. fig. 12a); but it is sometimes difficult 
to see this wall, because the gonidium lies so closely within it. 
It is a frequent occurrence for two or more gonidia to be found 
in close apposition (Pl. LV. fig. 11, & Pl. LVI. fig. 23, &e.) ; 
aud careful examination may be rewarded by the discovery of a 
delicate common wall running round them. In this way may be 
produced small masses of gonidia which may either break up by 
the destruction of this common wall, the gonidia rearranging 
themselves upon the Apiocystis-wall, or, owing to the former's 
persistence, may, as will hereafter be explained, remain connected 
even after great chages have been brought about in the Apiocystis- 
wall itself. In figs. 12 a-e, Pl. LV., an endeavour has been made 
to show this method of gonidial multiplication : both here, and also 
