8 
Elizabeth Acton. 
bottom and there gradually form resting spores before breaking 
up. But in freshly collected material, balls of this nature would 
probably be discarded or, at any rate, not examined ; and so the 
resting spores would be overlooked. 
II. Origin of the Ball-like Forms. 
Lorenz' in 1901 was the first to show that these ball-like forms 
are developed from isolated individuals and later Brand (loc. cit.) 
shewed that each species of Aegagropila could, given the necessary 
external conditions, exist in the different forms of thallus described 
as “ Rasen,” “ Polstren ” and “ Ballen” so that specific characters 
should he sought in the anatomy of the single plant rather than in 
the form of the thallus which is of quite secondary importance. 
The different forms of thallus and their mutual dependence on 
one another have been described in detail for Aeg. Sauteri by 
Wesenberg-Lund (loc. cit.) and since his account will probably 
apply in essential points to other species, a short summary of it is 
given here. 
In one of the creeks of Lac Soro the floor is covered with a 
thick felt-like layer composed of small separate individuals of Aeg. 
Sauteri. These individuals have a tufted radiating structure. The 
creek is not deeper than four metres in any part and has a soft 
muddy floor. 
A slight undulatory movement is communicated to the super¬ 
ficial layer of this felt by strong winds, causing the individuals to 
hook on to each other. In this way irregular packets are formed. 
The number of these packets increases towards the edge of the 
creek. The balls first appear at the edge of the felt where the 
action of the waves is strongest and the mud of the floor is 
somewhat coarser in texture. Near the edge of the creek where 
the depth is about one metre they can be found in quantity. 
These globular forms owe their existence to the mechanical action 
of the waves acting on a single individual of the felt or on packets 
of several individuals hooked together. The spherical form and 
radiating structure have been produced by the rolling and friction 
against the sandy bottom in the shallower parts where the action of 
the waves is more strongly felt. 
The close texture of the peripheral part is explained by the 
tendency which the alga has of replacing broken terminal joints 
by active lateral branching just below the injury, and by the 
1 J. R. Lorenz. Erganzungen zur Bildungsgeschichte der sogen. 
“ Seeknodet ” (Aeg. Sauteri Kg.). Verb. d. kais., kdnigl. zool. bot. Ges. Wien, 
Bd. 51, 1901. 
