26 INTRODUCTION. 



reproductive body, the cells are absorbed, at least the spores 

 issue by a rounded aperture which they constantly present at 

 this period. These corpuscles have offered me in this case an 

 ovoid form, and I have seen them without exception issue 

 forth, presenting in advance their colourless extremity. " 

 Of the many hundreds of specimens of Conjugate which I 

 have examined, it has never occurred to me to observe the 

 slightest change in the primary form of the spores or spo- 

 rangia ; what they really are seems to me a point yet to be 

 determined, nor have I ever seen the colourless extremity 

 referred to. 



The opinion of the production of the same species from two 

 organs so dissimilar in size and form as the zoospores and 

 spores are, is not so startling when the structure of these 

 is closely considered, as at first sight it might appear. The 

 zoospores being regarded as young cells of Conferva, con- 

 taining only one or two other incipient germs or zoospores, 

 and the spores as cells of larger growth, filled with 

 germs, or zoospores, which have arrived at or near their 

 maturity. 



The organ contained within each capsule of the different 

 species of the genus Vaucheria, I regard likewise as a sporan- 

 gium filled with zoospores, the horns near it being identical 

 in function with the vesicle already described. The ciliated 

 ovum formed at the extremity of the filaments of Vaucheria 

 is of course different from the capsular bodies. Having thus 

 given a general outline of the more interesting and leading 

 facts connected with the reproduction of the freshwater Alga, 

 we shall next proceed to the consideration of their structure 

 and modes of growth. 



The structure of the Conferva is exceedingly simple. An 

 outer membrane, transparent as water, invests a number of 

 cells, which exhibit under the microscope not unfrequently 

 a fibrous appearance. These cells do not communicate with 

 each other, although their truncate extremities are always in 

 apposition the one with the other. They contain a thick and 

 generally colourless fluid, in which are immersed, and some- 

 times scattered irregularly, as in the true Confervce, sometimes 



