4.7 & Frit sc h. — The Structure and Development of 
position, though evidently no longer in organic contact with 
the rest of the cell-wall. It is frequently so closely applied to 
the top cell, however, that it could be easily overlooked. In 
other cases it is cast right off and is found lying loose in the 
water. I observed the structure of the first ring in this 
species ; it agreed with the description given by Poulsen 
(loc. cit.), going over into the inner layer of the wall above 
with a gradual curve. I also followed its division into two 
layers and the casting-off of the outer one as a cap. In Oed \ 
stagnate as a rule no cap is cast off, as is sometimes also the 
case in the first-discussed species. In Oed. calcaremn I was 
not successful in finding a cap at the apex of the two-celled 
plants, although one is frequently found covering the top cell 
of four or five-celled individuals. It would seem as though 
this casting-off of the first cap depended to some extent 
on the shape of the apical cell ; when this is acutely rounded 
the cap is often cast off (cf. however Poulsen, ’ 79 , p. 5). 
3. Abnormal Development of the Young Plant. 
In the course of my investigations on the young plants of 
Oedogonium I came across a number of interesting abnormalities, 
which I will now briefly discuss. Fig. 26, d shows a young 
plant of Oed. stagnate , which, although consisting of only two 
vegetative cells, has already commenced to form sperma- 
tozoids (j-). I found this individual amongst other normal 
ones of the same species, scattered in between the adult fila- 
ments, from which the zoospores for their formation had been 
derived. These adult filaments were engaged in very active 
spermatozoid formation, there being five or six antheridia 
between almost each of the vegetative cells. In this point the 
young plant differed from the adult, for there were only two 
antheridia present in each group. The conditions were 
evidently very suitable for spermatozoid- formation, and hence 
probably the precocity of the individual figured. The lower 
group of antheridia are still developing, in the upper group 
one has already liberated its contents. Such an abnormality 
may show how the dwarf-males originated, for the smaller 
