1 80 DUBLIN NATITRAL HISTOEY SOCIETY. 



suppoi-t their side of the question. This Dr. Kinahan had most unequi- 

 vocally denied, and he was much surprised at such a statement, where 

 the specimens then exhibited showed the distinctions of the species so 

 plainly. He would even venture to retort the statement, as, if unsup- 

 ported assertion is an argument relied on by either side, it is certainly by 

 those who advocate the union of the species, as he hoped to show. 



Another fallacious statement brought forward was, that if Irish bo- 

 tanists had an opportunity of examining a wider field, they would be 

 likely to change their views. This certainly is mere assertion, for 

 any one who takes the trouble of examining the list of localities given 

 in the " Species Filicum" will see that independent botanists, who have 

 travelled, have, in different and remote parts of the world, all distin- 

 guished these two forms as species, so that, supposing them to be mere 

 varieties, the same modifying causes which exist in Ireland exist in 

 nearly every locality in which the ferns, or either of them, have been 

 found. Furthermore, in two localities in Ireland, and, doubtless, 

 there are many others, the two forms grow absolutely together — the 

 plants of each, though intermingled, being perfectly distinct. It might 

 be well to state that in a letter, received only this morning from Mr. 

 F. J. Foot, he states that, as far as Killarney is concerned, the two 

 species are met together, and in that station Dr. Kinahan might re- 

 mark that the finest specimens he had ever seen of both species occur. 

 Professor Harvey had borne testimony to the accuracy of the statements 

 as regarded these genera in Ireland and their seeming distinctness ; and 

 this testimony Dr. Kinahan looked on as peculiarly valuable, as Pro- 

 fessor Harvey is a staunch supporter of the unity of the species. If 

 these two are mere varieties of one another, how is it that both flourish, 

 and so abundantly, in the one locality ? and how is it that the circum- 

 stances favourable to one do not cause the transmutation of the other? 



The great argument rested on by the unity of the species advocates 

 is the existence of intermediate forms ; but what is meant by the term 

 *' intermediate form?" Have perfect specimens ever been exhibited which 

 would cause hesitation for a moment ? • Are any specimens known pos- 

 sessing both forms of involucre on the same plant ? or possessing invo- 

 lucres of a mixed character ? Till such are produced, or till it can be 

 proved that by any kind or amount of culture one can be converted into 

 the other, the argument of intermediate forms is inadmissible. True in- 

 termediate forms run into each other under cultivation. Dr. Kinahan 

 had examined these plants in innumerable stations in Ireland, and fre- 

 quently under cultivation, and must say he had never seen or heard of a 

 case. If by "intermediate form" is meant a specimen or plant in which 

 the figure and direction of the frond, or, as it is commonly called, the 

 habit, of the one species, is simulated by another, the character of the 

 involucre remaining constant, the union of the species, on that ground 

 only, must fail ; for all the essential characters are not identical. Is there 

 such a thing known as any two species widely differing in their cha- 

 racters, between which gradational species do not occur ? And are we 



