inO FBESmVATKR AI,(;.T!;. 



Conjugation, as the term implies, consists of the yoking together of two 

 contiguous filaments which, by some mysterious means, approach one 

 another and assume a position of sti'ict parallehsm. Pi-ojections are 

 then thrown out between opposite pairs of cells, and gradually increase 

 till they finally meet and foi-m connecting tubes. At the same time the 

 endochrome loses its spiral arrangement, and becomes an irregular, con- 

 fused mass. [Plate III., Fig. 14.] It then passes, as in Zygnema [Plate III., 

 Fig. 12] and Spiror/i/ra, [Figs. 13, 14,] into the opx^osite cell and there, 

 mingling with the contents of the latter, forms a round or oval spore 

 with distinct cellulose coating ; or, as in Mesocarpus [Fig. 15] and 

 Staurocarpus, [Fig. 16,] meets the contents of the opposite cell, which 

 move forward to join it, in the connecting tube, aud there fonns a 

 spherical or cruciate spore. 



A curious modification of this process occurs in some species of 

 Spirogyra, where the spores are formed not from the contents of two 

 opposite cells of different filaments, but by the union of those two 

 contiguous cells of the same filament, the mingling of which is 

 effected through a little tube bridging over, as it were, the septum 

 between them. [Plate III., Figs. 17 aud 18.] It is asserted by some 

 wi-iters that this phenomenon is abnormal, and occurs in species which 

 usually conjugate in the ordinary way ; but the writer has only once seen 

 the two processes occui'ring simultaneously in the same plant, and has 

 always observed this form of conjugation in specimens the proportions of 

 which stamp them as distinct species. 



The most striking point about the operation just described is the 

 assumption by the contents of the cells of different plants, or by those of 

 special cells in the same individual, of the opposite properties upon which 

 depend respectively the powers of imparting and receiving fertilisation, 

 although the most careful scrutiny under the highest powers of the 

 microscope fails to reveal the least diffei'ence in their condition. It has 

 been stated that this polarisation, as it may fitly be tei'nied, in the ordi- 

 nary form of conjugation, is capricious, the cells of the two filaments 

 assuming indiscriminately these converse functions, but in the many 

 hundreds of specimens which we have examined and mounted, we only 

 remember finding one exception to the rule that all the cells of one 

 conjugating filament assume "male" and those of the other "female" 

 sexual functions ; this exception occurred in the specimen already 

 referred to, in which conjugation of contiguous cells of the same 

 individual also took place, and in this case the spores formed in one 

 filament were large, while those in the other and alongside of the cells 

 which had discharged their contents were much smaller, and apparently 

 imperfectly developed. 



It now remains to answer the two last questions which we proposed 

 in the outset, viz. :— How are the Algaa best collected? and how should 

 observations on their structure, Ac, be recorded? 



The larger filamentous Algas are best brought home in small glass 

 tubes of thick glass well annealed. 



A compact foi-m of collecting apparatus coiisists of a number of 



