118 SIPHOPHYCES. 
At this stage a septum is suddenly formed at the base of the 
sporangium, which is henceforth an independent cell, completely 
separated from the parent tube. Even before this septation there may 
be noticed in the rostrate elongation directed towards the hornlet, the 
gradual accumulation of a colourless fine granular substance, of the same 
nature as that with which the wall of the parent tube, and the 
sporangium is lined on the inner surface, which has already been termed 
the “cutaneous layer.” This accumulation in the fore part of the 
rostrum is continued after the formation of the septum between the 
sporangium and the tube, and in consequence of its continued increase, 
the remaining contents of the sporangium are by degrees pushed back 
towards the base. Whilst these phenomena are being manifested in the 
sporangium, the hornlet also undergoes remarkable changes. In its 
apex, the contents, owing to the disappearance of the chlorophyll, have 
become almost colourless, more or less. Thus the point of the hornlet, 
like that of the sporangium, appears at this time to be filled with a 
colourless substance, which is nvt constituted by an accumulation of the 
cutaneous layer, but manifestly arises from a molecular change 
associated with an alteration of form and colour in the contents pre- 
viously existing at the apex. So soon as the contents at the point of the 
hornlet have thus become colourless, they appear to be constituted of a 
very fine-grained granulose mucous substance. As soon as the trans- 
formation of the contents has taken place, the colourless apex of the 
hornlet is suddenly separated from the lower green portion by a septum, 
and is thus transformed into an independent cell, without communication 
with the parent tube. The point at which the septum is formed is not 
very determinate, the portion cut off being sometimes larger, sometimes 
smaller. 
After the formation of the septum in the hornlet the colourless mucous 
in its apex gradually assumes a more deterininate form, and at 
this time a large number of minute, perfectly colourless, rod-like 
bodies may be readily perceived crowded together irregularly, and 
as it were imbedded in the surrounding mucous. Close observation 
will disclose an indistinct movement exhibited even thus early 
by some of the little rods, from which their destination may be 
anticipated. 
This perfecting of the hornlet coincides with that stage of development 
of the sporangium at which the accumulation of the cutaneous layer in 
the anterior part of the rostrum has attained its greatest extent, and 
these conditions immediately precede the act of impregnation, which is 
effected in the following manner :— 
The pressure within the sporangium, especially in the direction of the 
rostrum, becomes greater and greater in consequence of the continued 
increase of the cutaneous layer in the fore part, until ultimately the 
membrane is ruptured exactly at the point of the rostrum, and allows a 
portion of the cutaneous layer to escape. The extruded portion 
becomes detached, and assumes the character of a drop of mucous, which 
remains lying near the openirg of the sporangium, and ultimately 
perishes. The accumulation of the cutaneous layer in the fore part of 
the rostrum, and the escape of a portion of it, are merely the mechanism 
by which the opening is produced in the sporangium destined for the 
admission of the spermatozoids, Immediately after the formation of 
this opening in the sporangium, and in remarkable coincidence with 
the escape of the cutaneous layer through the rostrum, the hornlet opens 
at the apex, and pours out its contents. Innumerable excessively minute 
rod-like corpuscles ( 005 mm.), mostly isolated, escape at once through 
the orifice. Those already isolated exhibit an extraordinarily rapid 
movement in all directions, and those still imbedded in the mucous do not 
become detached until afterwards, when they follow the others with. 
equal rapidity. The field of view is soon covered with mobile corpuscles, 
