118 SIPHOPHYCE^:. 



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 horulet 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 not 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 determinate form, and at 

 this time a large number of minute, perfectly colourless, rod-like 

 bodies may be readily perceived crowded together irregularty, 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 sperm atozoids. Immediately after the formation of 

 this opening in the sporangium, and in remarkable coincidence Avith 

 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. 



