of the Freshwater Alga. 23 



the inability wliicli lias hitherto been felt to explain in what way the 

 intermingling of bodies in all respects so similar in organization 

 and appearance as the bright granules of the Confervse seem 

 to be, can be regarded as giving origin to fertility; secondly, it does 

 away ^\iththe anomaly, which has always appeared to me so strange, 

 that a combination of the matter of two cells should invariably 

 take place in certain divisions of the Confervoid tribe of produc- 

 tions, while in other divisions of the same tribe, which could not 

 be supposed to differ fundamentally from the former, no such phse- 

 nomenon has hitherto been recognised, by showing that this com- 

 bination is not an essential to the perpetuation of the species; 

 and thirdly, it explains the permanence of species which have 

 perished before miion of the endochrome and formation of spores 

 have taken place. 



I do not wish to assert that the above opinions rest in their 

 entirety upon conclusive facts, but would merely remark that they 

 are opposed to no kno\Aii established fact in the history of the 

 Confervpe, and that instead of adding to the difficulties which en- 

 velope some points in the physiology of these productions, they 

 have the advantage of removing several obscmities. Their true 

 value must however be developed by extended observation*. 



I have detected cji:oblasts in numerous Zygnemata, but the best 

 species in which to examine them are the larger kinds, such as 

 Zygnema ma.ximum, Z. nitidum and Z. belle. Of the genus Vesi- 

 culifera I have also found it in several species : they cannot always 

 be seen in these, owing to the cells not being transparent ; I doubt 

 not however but that they are general in it as well as in other 

 genera of Algse, whether marine or freshwater. For its appear- 

 ance in this genus, see PI. I. fig. 6. 



In conclusion it may not be out of place here to observe, that 

 Mr. Bowerbank was enabled to detect in the Zygnema which I 

 transmitted to him, Z. nitidum, two other minute organs, both 

 of which I have since myself more than once observed ; the one 



* Since the above passage was written I liave several times encountered a 

 Zygnema, in which all the spores are formed without either union of the fila- 

 ments or commingling of the contents of two cells ; that is, they are formed 

 separately in each cell. This observation, the accuracy of which does not 

 admit of the slightest doubt, is therefore, in a high degree, corroborative of 

 the opinion that the central organ in each cell oi Zygnema and other Con- 

 fervse is that by which fertilization of the zoospores is effected. To this 

 species I have given the name oi Z. mirabilis. In a species of the genus 

 Mougeotia, M. notahiUs, spores are also formed in each cell. Another fact 

 may be here alluded to, which confirms in a manner no less strong this opi- 

 nion, which is, that although tlie filaments oi Mougeotia geiwflexa, M.com- 

 prcssa and their allies conjugate even without the intervention of transverse 

 tubes, yet no transference of endochrome ever takes jilace and no formation 

 of sporangia occurs. This curious particular is the result of continued ob- 

 servation for two successive years. 



