38 NATURAL SCIENCE. January. 



few, in discussing the arguments here ably presented by Professor 

 Cope. 



First, the author attempts to show that variations are definite and 

 in determined directions. That there are hmits of variation in each 

 species may be admitted, whether the Hmits be wide or narrow, 

 whether they be due to obvious physical and chemical conditions or to 

 characters impressed on the race by ancestral history. That allied 

 species, or the varieties of a species, and especially geographical sub- 

 species, observe a successional relation to each other, is a fact that no 

 one need hesitate to accept after reading the numerous instances here 

 brought forward. A lizard, to select but one example, does not jump 

 from a longitudinally striped to a transversely banded form, but the 

 two are connected by intermediate series of broken stripes, spots, and 

 broken bands, a circumstance tending to show that one has been 

 derived from the other ; and when we enquire which it is that has been 

 derived, we cannot ignore the further fact that forms banded in the 

 adult have young that are striped and pass through a spotted stage. 

 Nor is this relation confined to superficial characters; it appears no 

 less plainly in the teeth of mammals, in the shoulder-girdles of frogs, 

 and in the arm-loops of brachiopods. We accept all this ; but we 

 accept it as a statement of the trend of evolution, not as expressing 

 the direction of variation. With the exception of a paragraph quoted 

 (without reference) from a paper in Natural Science by the Rev. G. 

 Henslow, there is no attempt to show that all the offspring of any 

 individual vary, if they vary, in one direction, and that the direction is 

 constant for all individuals of a species. Indeed, it is hard to see 

 why the main facts detailed by Professor Cope in this chapter cannot 

 be explained just as well on a hypothesis of natural selection, 

 although, in the enforced absence of evidence, the explanation would 

 be worth just as little. 



The next chapter deals with phylogeny, especially with various 

 lines of descent within the Vertebrata, which, by reason of definite 

 palaeontological evidence, are better known than any others. The 

 position of these facts in Professor Cope's argument appears to be 

 stated in this paragraph: — " Examination of all these genealogical 

 lines reveals a certain definiteness of end and directness of approach. 

 We discover no accessions of character which are afterwards lost, as 

 would naturally occur as a result of undirected variation. Nor do we 

 discover anything like the appearance of sports along the line, the 

 word sport being used in the sense of a variation widely divergent from 

 its immediate ancestor. On the contrary, the more thorough becomes 

 our knowledge of the series, the more evident does it become that 

 progressive evolution has advanced by minute increments along a 

 definite line, and that variations off this line have not exerted an 

 appreciable influence on the result." This statement, just as the 

 preceding ones, may be accepted ; but, equally with them, its bearing 

 on the question is not obvious. In saying that there are no accessions 



