256 PROGRESS OF MICROSCOPICAL SCIENCE. 
of zoospores, which soon come to rest and grow into new plants, as 
in the case of the macrozoospores. The latter it appears are more 
common in winter and spring, and were produced abundantly on 
thawing tufts which had been frozen, while the microzoospores are 
more common in summer. The most curious fact observed by Dodel 
is that those microzoospores which, for any reason, do not succeed 
in conjugating, grow at once into new plants just as in the case of 
the macrozoospores. In other words, the sexual process is reduced to 
the direct union of two bodies so similar that it is impossible to dis- 
tinguish one as male and the other as female, and furthermore these 
bodies, if not placed in conditions favourable for conjugating, can at 
once grow into new plants. It would be difficult to find sexuality of 
a lower grade than this, where each sexual organ is also capable of re- 
producing the plant by non-sexual growth. We would recall the case 
of Eurotium herbariorum mentioned by De Bary, where, of the several 
male organs (pollinodia) only one succeeds in coming in contact with 
the female organ, yet all, after the fertilization has taken place, 
continue to grow and take part in the formation of the sac which 
eventually encloses the spores. With very rare exceptions in the 
Thallogens, the male organ at once atrophies after fertilization has 
been accomplished. 
A New Parasitic Green Alga.— Nature, of March 8, says that not 
very long since it was thought that the want of chlorophyll deter- 
mined the parasitism of plants, and it is still true that the want of 
this green colouring substance serves to distinguish between fungi 
and alge. It is also true that the former need already-formed carbon 
compounds, but it is still thought that chlorophyll-bearing plants not 
only do not require to find these compounds ready formed, but that 
they are absolutely unable to assimilate them. It was therefore a fact 
of great interest when Professor Cohn described some years since 
(1872) a perfectly new chlorophyllaceous alga,* which he found 
living as a bright emerald green parasite in the thallus of duck-weed 
gathered at Breslau. For this the genus Chlorochytrium was esta- 
blished, and C. lemne was the only species until at a late meeting of 
the Dublin Microscopical Club, Professor E. Perceval Wright ex- 
hibited and described a second species found growing and developing 
itself in the mucilaginous tubes of a species of Schizonema, collected 
on rocks at Howth, near Dublin, between high and low water marks. 
There can be no question as to the parasite on the diatom bein 
different from that on the duck-weed, while there is but little difficulty 
in placing it in Cohn’s genus. Smaller in size its emerald lustre is 
scarcely if at all less than the fresh-water species, and like it its 
development has not been traced farther than the production of 
ZOOSpores. 
The Structure of Distoma sinense.—This is very fully given in a 
paper by Dr. W. Macgregor, of Fiji, which appears in the ‘ Glasgow 
Medical Journal’ (January 1877), and to which is appended a note by 
* “ Ueber parasitische Algen,” in ‘ Beit. zur Biol. der Pflanzen,’ Bd. I. Heft 2. 
