272 NATURAL HISTORY SOCIETY OF DUBLIN. 



the septum of a simply vegetating cell, divides the mother-cell into two 

 very unequal daughter- cells, the larger of which becomes externally 

 expanded. This larger expanded daughter-cell is that one which hears 

 the extension joining it to the other opposite conjugating cell, and is 

 constantly the receiving cell — that is, the one ultimately to contain the 

 zygospore. Its sister-cell — the smaller one — remains sterile, being shut 

 off from participating in the conjugation. The other opposite conju- 

 gating cell also becomes divided by a septum into two daughter-cells, a 

 short and a long one ; but in this instance it is the shorter daughter- 

 cell to which the extension joining it to the other conjugating cell be- 

 longs, and this cell is in conjugation constantly the giving cell ; its 

 sister-cell — the larger one — remains sterile, being shut off from par- 

 ticipating in the conjugation. The shorter or giving cell is itself some- 

 times again divided into two, one of which daughter-cells is shut off 

 from participating in the conjugation. Speedily the contents of the two 

 connected cells become increased in quantity and density, so as more 

 nearly to fill the cells, quite unlike the sparse pale (yellowish-green) 

 and narrow irregular bands formed by the endochrome of the simply 

 vegetative cells. The contents of the two conjugated cells now become 

 contracted from the cell-wall; the intervening septum of the tubular in- 

 osculated connecting processes becomes resorbed ; the contents of the 

 smaller of the two passes over, as in Spirogyra, and becomes formed, 

 within that of the other, incorporating with its contents, into a zygospore. 



Here, then, is a conjugation between two cells not morphologically 

 equivalent, but which are evidently specialized structures. Here the 

 giving and receiving cells seem to be as morphologically distinct as in 

 (Edogonium curvum, in which the antheridial cell gives birth to a single 

 epermatozoid, not much smaller than the oospore, the main distinc- 

 tive circumstance being, that in the latter the fertilizing cell is ciliated, 

 making its exit from one, and its entrance into the other, parent cell by 

 an opening in each, whilst in the former neither is ciliated ; and, be- 

 sides, the parent cells being apart in the one, and joined together by a 

 firm inosculation in the other. 



It being admitted, then, that this case is one of a true generative 

 process, the reproductive elements being seemingly well differentiated 

 as germ-cell and sperm-cell, the transition downwards through the va- 

 rious forms of Conjugate is easy and natural to our Mesotaenium and 

 Cylindrocystis ; and it seems to compel the admission that the process in 

 all is a manifestation of one and the same phenomenon, with one and the 

 same import. 



But it may be further objected, that in many of the Conjugatae 

 spores or spore-like bodies very similar to the true zygospores, and 

 from which young plants may be developed, are formed without any 

 conjugation at all. However, it seems to me that these bodies may 

 bear a relationship to the ordinary zygospores, the same as that of the 

 ordinary zoospore of (Edogonium and Bulbochsete to the four zoospores 

 evolved from the fertilized oospore ; and both bear to the plants which 



