60 Adenocystis, Alaria and Saccorkiza. 



forward a third view, which is just as likely to be true as the others, and 

 certainly is very ingenious. She says: ' My own view of the matter is that 

 the two forms of conceptacle are of equal antiquity, and were a later 

 development in the ancestors of the Fucacea than the reproductive organs ; 

 therefore I consider neither form a development of the other, and the fact 

 that one conceptacle contains reproductive organs, the other nothing but 

 paraphyses, is an interesting point, but does not bear on the phylogenetic 

 history of the conceptacles themselves.' I know so little about the 

 ancestors of the Fucacece, that I must be content with a respectful attitude 

 towards this statement. 



As Prof. Bower has pointed out, the development of both conceptacles 

 and cryptostomata is the same. To quote his words, it ' is preceded by 

 the decay of one or more cells which occupy a central position with regard 



to the changes which follow The cell or cells which decay are in 



all cases members of a linear series.' These words appear to me to be the 

 true guide of those who investigate the development of such bodies. 



When one comes, however, to compare the process as it takes place 

 in Splachnidium the process of making a conceptacular body for the 

 development, not of oogonia and antheridia, but of zoosporangia we 

 find a slight but noteworthy modification. The process is so nearly allied, 

 and the result achieved so similar, as to furnish material for direct com- 

 parison. Prof. Bower (loc. cit., p. 47) acknowledges the impossibility of 

 finding a parallel instance while speaking of the destruction of initial cells. 

 There is in Splachnidium not a parallel instance, but a closely comparable 

 one. The peculiarly modified initial cell of Splachnidium is homologous 

 with the initial cell of the Fitcacece but it persists. ' The epidermal cells ' 

 (page 5, ante) ' lying around it undergo division, and the neighbouring 

 cortical cells increase in size. These causes combine to place the initial 

 cell in a depression (plate II., fig. 7). Hairs arise from the youngest 

 epidermal cells, while others which were formed earlier surround the 

 mouth.' In Fucus, it will be remembered that hairs are not produced 

 until the formation of a young conceptacle with an ostiole, while the 

 initial cell has decayed. The hairs in the conceptacle of Splachnidium 

 are long, septate, and unbranched, increasing in length by successive 

 divisions at the base, and giving the young conceptacle the appearance 

 of the cryptostomata of the Fucacea. The sporangia are developed later. 

 We have in fact in this type a sorus of sporangia and paraphyses com- 

 parable with those of Laminaria, rolled up and definitely limited in a 

 conceptacular body, produced, not exactly in the same manner as the 

 Fucaceous conceptacle, but after another manner directly comparable 

 with it. 



