LINNEAN SOCIETY OF LONDOIST. XUl 



varieties of one species are absolutely fertile, whilst hybrids of two 

 species, unless fertilized by one of the original parents, are always 

 sterile ; or,in other words, that this character is absolute for the test- 

 ing of species and varieties. Opposed as this would seem tp Mr. 

 Darwin's views, the contradiction is, in some measure, more verbal 

 than real. M. Grodron makes the definition of the term ' species ' 

 to depend on this one physiological character, in preference to any 

 combination of characters, external, structural, or physiological. If 

 two supposed species (for example, Datura Stramonium and D. Ta- 

 tuld) produce fertile crops, then they are varieties only, not species. 

 If two supposed varieties (for example, Dlplacus aurantiaciis and D. 

 puniceus) produce crosses uniformly sterile, then they are species, 

 not varieties. But these are not strong exceptional cases, nor does 

 M. Grodron deal with any such ; he was probably not awa^re of them, 

 not having met with any in the limited range of species he experi- 

 mented upon ; or if anything in his experiments did turn out con- 

 trary to his expectations, he would attribute it to some failure 

 owing to deficiency in his precautions. So again, although he ob- 

 served great variety in the degree of apparent perfection or de- 

 fects in both the male and female organs of hybrids, the idea of 

 difterent degrees of sterility does not appear to have occurred to 

 him ; and, on the whole, his memoir, notwithstanding a number of 

 facts and observations of considerable interest, cannot be said to 

 have contributed much, if anything, towards the confirmation or 

 refutation of Mr. Darwin's views. 



M. Naudin's memoir is of a very different character. It is not 

 yet published in extenso ; but the second portion, including the dis- 

 cussion and general results of his experiments, is inserted in the 

 same Number of the Annales des Sciences Naturelles (ser.4,vol. xix. 

 p. 180), and the principal facts it contains are very clearly pointed 

 out in an article in the ' Natural History Heview ' (1864, p. 50). 

 This is quite sufiicient to enable us to appreciate the great value 

 of his labours ; and having moreover, on various occasions, had 

 personal opportunities of witnessing the zeal, care, and assiduity 

 with which he pursues any subject that he takes up, I cannot but 

 concur in the high eulogium conferred on his memoir by the com- 

 mittee appointed to award the prize. It is therefore of consider- 

 able importance that his conclusions should, in the main, so closely 

 coincide with Mr. Darwin's, although independently formed. He 

 especially insists on the great diversity in degree of sterility, and 

 the impossibility of drawing, by means of this or any other cha- 

 racter, any positive line of demarcation between a variety, a race, 



