102 REPORT 1856, 



being due to climatal or other external causes exercising a permanent influence through 

 a succession of generations. Hence it was recommended, in the case of such species 

 as have others closely allied to them but supposed to be probably distinct, to endeavour 

 to trace the effect of such causes. Many facts bearing on this question were thought 

 to be already on record, only scattered over various works and periodicals, which 

 required to be collected under one head; while a far larger number were wanted in 

 order to arrive at any certain conclusions admitting of such generalization. These 

 last must principally be sought for at the hands of travellers or naturalists stationed 

 in different parts of the world, whose comparative observations on the same species, 

 as found in diflferent regions and latitudes, would prove of great value. 



In this communication the author restricted his remarks for the most part to the 

 species adopted in zoology. It was urged especially that we should endeavour to 

 work out the history of those exotic animals which either appear identical with, or 

 which closely approximate to, European forms, and observe whether, between two 

 nearly allied species inhabiting remote countries, there cannot be discovered inter- 

 mediate forms, or as they have been termed transition species, serving to show the 

 passage from one species to another, and so proving all to be the same. Or, if such 

 cannot be detected in any of the intervening parts of the globe, inquiry should be 

 made whether the exotic form is never found in any transition state in the particular 

 country it inhabits. It was remarked that it does not follow, because the European 

 race never acquires the distinguishing character of the exotic form, that the latter 

 may never so vary as to become identical with the former. 



But it was added, that before we can hope to clear up the doubts which hang over 

 a large number of exotic species, we must be better acquainted with the European 

 species themselves to serve as a standard of comparison with all others. Even in the 

 case of some of our most common birds, and the same is true in every other class of 

 animals, there are several different races, or sub-species as some call them, or real 

 species as accounted by others, inhabiting either the same or different countries on 

 the continent, each showing some shght though constant peculiarity of character, 

 but on the whole so generally similar, that we are at a loss, in the present state of 

 our knowledge, whether to refer them to one or more than one original stock. It 

 was thought that the endeavour to remove some of the difficulties which attend this 

 question would prove more serviceable to zoology than adding to our already over- 

 loaded lists of names, one-half of which would probably in the end sink to mere 

 synomyms, increasing the confusion. We alone advance the philosophy of the 

 science, when we are not content with registering a new species, or subdividing an 

 old one ; but when we seek to ascertain the origin and nature of species themselves, 

 their geographical range, the influence they receive from the particular circumstances 

 under which they live, the limits within which they may vary, without having their 

 essential diflferences destroyed, — and the degree of permanence stamped upon some 

 of these variations, through the slow operation of local and climatal causes over a 

 long period of time. 



The author, in allusion to the doubts entertained by some with respect to species 

 in general, stated his opinion that there was nothing to contradict the belief 

 that they had a real existence in nature, and that all the individuals belonging to 

 the same species had emanated from a single stock, or in other words, that there 

 had been for each species but one centre of creation. He considered that the case 

 of hybrids, so far from proving anything to the contrary, only demonstrated the 

 reality of species the more plainly ; for he believed that strictly hybrid plants had 

 never been known to reproduce themselves beyond two or three generations at most, 

 while there were not more than one or two well-authenticated instances of hybrid 

 animals producing offspring at all, excepting with one of the parent species, to which 

 in this way, the hybrid, making continually a nearer approach, was gradually brought 

 back. He regarded this as a clear indication on the part of nature that there is a 

 barrier separating certain forms, or collections of forms, from certain others, which 

 shall not be ordinarily passed, and never passed, without those who pass it, being, 

 so to speak, sent back in the end. Unless we ground our notions of the species on 

 this law, we in vain attempt a definition of it at all. If we once hold that species can 

 intermix through an unlimited succession of generations, since no species under such 

 circumstances could preserve its distinguishing characters for any length of time, 

 it is equivalent to saying that species have no existence at all. 



