IXX ' PROCEEDINGS OF THE 



argumonts, the wliolo appears to me to be so purely siieculative, 

 with the total absence of ascertained facts to rest any theory upon, 

 that it seems out of our province to dwell upon it. 



The really important part of Ilaeckel's work appears to be the 

 second, or morphogenetic volume, or development of the theory of 

 affinity derived from a common descent, which, as he truly says, 

 has been more or less broached by various philosophical naturalists 

 of the present century, but to which Darwin has first given us the 

 key. The methodical views here displayed, notwithstanding their 

 speculative tendency, require more study than I have as yet been 

 able to bestow upon them ; but a perusal of the principal chapters 

 points out as the most remarkable parts the classification of the dif- 

 ferent modes of reproduction and development with reference to the 

 six form-individuals distinguished in the first volume, the metho- 

 dical exposition of the Darwinian laAvs of inheritance, variability, 

 and selection, and the attempt at a classification of organisms ac- 

 cording to what may, with more or less of plaiisibility, be con- 

 jectured as to their descent and succession through the various 

 geological epochs. In all these eases the chief defect is, perhaps, 

 too much of absolute dogmatism, without distinction of those dif- 

 ferent degrees of certainty, probability, or doubt so admirably dis- 

 cussed by Darwin. In the classification, the establishment of the 

 intermediate cla.ss of Protista, for those comparative^ simple orga- 

 nisms which appear to connect the lower animals with the lower 

 plants, is an attempt, which may or may not be successful, at sup- 

 plying more definite lines of demarcation than those which arc now 

 vainly sought for between the animal and vegetable kingdoms. 



The repeatedly discussed question of species is here treated at some 

 length. We can all argue as to the identity or distinction of species ; 

 but none of us can give a really definite reply to the question 

 "What is a species ? Those who insist on the absolute fixity of the 

 limits of species can give us no rule for the ascertainment of those 

 limits which does not occasionally break down ; those who deny 

 that there are limits to species yet constantly speak of species as if 

 they had limits. The object of a paper recently communicated by 

 Darwin, and now printing in our journal, is to show that Primula 

 vulgaris, P. veris, and P. elatior, Jacq., are distinct species ; and 

 Haeckel himself has frequently to speak of species like other natu- 

 ralists. He argues, as others have done, that all morphological and 

 physiological tests of species fail in particular instances, that the 

 ordinary idea of a species is purely arbitrar)'^ and artificial (ii. 



