8 INTRODUCTION. 



this formation. Frequently it is so concealed beneath the 

 green gi'anular mass, that it cannot be seen without some 

 trouble : sometimes it lies near to or between both divisions 

 of the green mass, and then more easily comes into sight ; but 

 at the same time it is observable, that it remains unaltered, 

 and is foreign to the whole of the slimy structure described 

 above. The latter seems only so far to have a relation to it, 

 that its point of concentration is always at the place where 

 the nucleus lies, and indeed between it and the walls of the 

 mother cell." 



Subsequently, the two masses become divided into four, 

 and the reticulated appearance produced by the spreading of 

 the masses subsides into radii, which are similar in aspect to 

 those emanating from the cytoblast in the Zygnemata, each 

 arising separately from the masses, and terminating on the 

 inner surface of the cell. Finally, each radiated mass becomes 

 a perfect spore or cell, separated from each other by distinct 

 cellular walls, in which changes similar to those just described 

 take place for the production of other spores. The great 

 similarity in the structure of the incipient spores in the genus 

 Anthoceros with that of the radiated organs in Zygnema, 

 would lead to the supposition that they were identical in their 

 nature ; so far, however, from this being the case, I consider 

 that all analogy between them terminates with the outward 

 resemblance. The difficulties in the way of regarding the 

 structure in Zygnema as an incipient germ or spore, appear to 

 me to be insuperable ; for the question would immediately 

 arise, wherefore is it, that since the contents of tioo cells 

 generally go to fonn a single spore in the genus Zygnema^ 

 and since this radiated organ is 2:)resent in every cell, that the 

 one is suppressed, while the other is destined to give birth to 

 the future Zygnema 9 Supposing, however, a satisfactory 

 solution of this difficulty to have been made, still another 

 arises. It is far from being an incontrovertibly established 

 fact, that the elliptical body formed in Zygnema by the con- 

 centration of the matter of two cells, and usually denominated 

 a spore, does really contain but a single germ. It is far 

 more consistent with known facts to suppose that they are 



