IN VEGETABLE BIOLOGY. 263 
good fortune of 1885, and, as time permitted and a continuous 
supply seemed available, part of the bygone year has been 
devoted to this interesting type, with results which it is pro- 
posed to describe in the following pages. 
In his * Gattungen einzelliger Algen’ (1849) we find the first 
description and figures * of Apiocystis Brauniana, at the hands of 
its discoverer, Naegeli. The spheroidal zoospores of this alga fix 
themselves by their anterior colourless end, usually upon a thread 
of Cladophora fracta, and clothe themselves with a claviform 
membrane, constituting a sac. The zoospore then divides in a 
plane coinciding with the axis of the sac, the two daughter cells 
becoming four, then eight, and so on till their number is thirty- 
two, after which numerical regularity ceases. This process may 
continue until as many as sixteen hundred cells are formed ; 
these lie upon the walls of a large sac, which has now become 
stalked. The cells are at first disposed uniformly upon the wall 
of the sac; but afterwards they lie im several layers. Division 
takes place in all directions of space. Naegeli also notes that 
the cells of old sacs are at times disposed eight together in a ring 
—the result of threefold division : of these eight, four are at first 
internal to the others, but they afterwards move so as to lie in 
the same plane with them. Zoospores escape through an opening 
in the wall of the sae; but there is no relation between size of 
the sae and zoospore-emission, which may take place from small 
sacs. The cells, he adds, usually lie quite separated from each 
other, for they invest themselves with a wall; although it some- 
times happens that only the second or third generation does this, 
the result of which is frequent grouping of the gonidia into 
masses of four or eight surrounded by a common envelope. A 
sinall form, linear or narrowly claviform, Naegeli distinguishes as 
the variety Zinearis ; and he also says that during the autumn the 
sacs are sometimes covered with delicate cilia. From this last 
fact it is clear that he must have had in view the above-mentioned 
ciliated form, which he regarded as merely a phase of the non- 
ciliated. In this opinion I entirely coincide ; and comparison of 
the accompanying figures with those of Naegelr's work will, it is 
hoped, leave no doubt upon any mind as to the propriety of this 
course, 
But scant references to Apiocystis are to be met with. It is 
* Naeg. Gatt. einzell. Algen, p. 67, tab. 1i. A. 
