336 Zoological Society : — 



is requisite of the bearing of this supposition upon another subject, 

 whereon Mr. Darwin's hypothesis of selection by means of the 

 struggle for existence has produced much controversy, namely, the 

 evidence of the " stone-book." That, if a new species can be formed 

 at all by "natural selection," it can be only as the ultimate result of 

 a long balancing of rival tendencies, ending in the preponderance 

 of one side, Mr. Darwin admits. It follows, as he also admits, that 

 each new species, if thus formed, must have left behind it a long trail 

 of intermediate forms between itself and the species whence it arises. 

 Now, we do not find this "trail ; " the links are wanting iu many 

 cases ; and Mr. Darwin's explanation of their failure is, that they once 

 existed, but that the evidence of their existence has either not yet 

 turned up, or has been altogether swept away. 



Other eminent geologists have questioned the probability, if not the 

 possibility, of this total sweeping away of the links wanted to bind 

 together, upon Mr. Darwin's sujjposition, the forms known to have 

 existed. I do not propose to enter into this controversy, but only to 

 remark that, whatever dithculty may arise from the absence of inter- 

 mediate forms in tracing connected lines of descent of the diflFerent 

 forms whose existence has been ascertained, it is most materially di- 

 minished on the hypothesis of typical selection, — (1) because the 

 advance in each case will be always in the same direction, and there- 

 fore the interval between one marked form and another will be indi- 

 cated by much fewer steps than are required on ]\Ir. Darwin's 

 supposition, even if each step be very gradual; (2) because it is con- 

 sistent with our present experience, tjiat a very considerable amount 

 of chano-e may take place in animal or vegetable organisms at once. 

 I will refer only to General Tom Thumb, and the Giant whose 

 skeleton is preserved in the College of Surgeons, in proof of the im- 

 portant departures from the ordinary human scale of proportion 

 which may be produced at one birth, under the ascertained laws of 

 life. Now, suppose individuals, male and female, characterized by 

 the possession of forms thus departing from the general human 

 standard, to be selected to constitute a new human species, forming the 

 centre of variations extending on all sides of the type thus manifested, 

 and the process to be repeated three or four times, by transitions of 

 equal magnitude on each occasion, in both directions ; we should 

 arrive at forms almost as distinct from each other as Swift's men of 

 Lilliput and Brobdingnag. And yet the intermediate variations might 

 succeed each other at short intervals, and leave but scanty traces of 

 their existence in any geological record. The Lilliputian and Brob- 

 dingnagian students of geology might thus find it as difficult to 

 connect their own history with that of the present race of mankind, 

 by geological evidence, as we find it to trace the descent of Teleostean 

 fishes, or Saurian amphibians, by the same records. 



The conception of "typical selection" seems also to elucidate 

 another subject, not altogether unencumbered with difficulty on 

 Mr. Darwin's hypothesis, namely, the disappearance of types. If 

 one species is educed out of another by a modification of the sexual 

 character of some particular variety of the first, whence it acquires a 



