ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 
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Their number was generally less in the earlier than in the later antherids. 
Their escape from the antherid takes place always in the same way. 
The lid-cell becomes detached ; and the ring-cell then, by its swelling, 
exercises a pressure on the contents of the antherid, by which the special 
mother-cells are pressed out of it. In these lie the antherozoids coiled 
up spirally and enveloped by their cilia. After a short time swelling 
causes the membrane of the mother-cell to rupture, and the antherozoid 
escapes. The activity of the antherozoids continues for a period of from 
20 to 55 minutes, according to the species ; the most favourable tempera- 
ture is between 15° and 28° C. ; both higher and lower temperatures are 
unfavourable. It is dependent also on the presence of free oxygen and 
on light. 
The proportion of malic acid in artificially prepared solutions which 
excited the sensitiveness of the antherozoids was uniformly, for all 
species, about 0 - 001 per cent. Neutral salts of malic acid produced 
similar results. Their sensitiveness attains its maximum at the moment 
of escape from the mother-cell. The balls of mucilage which are ejected 
from the ripe archegone exercise precisely the same attractive force on 
the antherozoids ; these bore through them in order to reach the neck of 
the archegone. As a general rule three large balls are first of all 
ejected, and this may be followed by the ejection of smaller portions. 
The mucilage-balls of any species appear to exercise precisely the 
same attraction on the antherozoids of any species, even belonging to a 
different genus ; so that antherozoids of one species may freely penetrate 
into the central cell of a different species of fern ; but here their progress 
ends ; there appears to be a mechanical difficulty — though of what kind 
has not been ascertained — in the way of their coalescence with the 
oosphere of a different species ; so that hybridism is very rare in ferns. 
A large number of antherozoids enter the central cell, but in no case was 
more than one seen to coalesce with the oosphere ; many of those which 
enter the central cell later again force themselves out of it, to be suc- 
ceeded in their turn by others. The coalescence takes place in the way 
described by Strasburger ; the antherozoid passes through the hyaline 
spot of the oosphere into its interior, and there very soon becomes 
indistinguishable. 
Sensitiveness of the Filaments of Mucorini.* — M. F. Elfving has 
made a series of observations on the sporangiferous filaments of 
Pliycomijces nitens, which are extremely sensitive to light and to gravita- 
tion. He also records the remarkable fact that they are attracted by a 
plate of iron or steel of any description, placed at a distance of several 
centimetres, curving towards it when in a state of active growth. Zinc 
and aluminium exercise but little influence ; platinum, gold, copper, 
lead, tin, and nickel none at all. He claims also to have determined 
that the attraction is not the result of magnetism, nor of electricity, nor 
of luminous or caloric rays, the phenomenon taking place equally in the 
dark and at ordinary temperatures. It appears to be a specific property 
of the metal. Combinations of iron, such as magnetite, haematite, and 
potassium ferrocyanide, are without effect ; but similar results are pro- 
* Ann. de l’lnst. Pasteur, 1800, See Bounier’s Rev. Gen. de But., iii. (1891) p. 3G‘2. 
