W. B. Scott — Variations and Mutations. 361 



etwas abweichende Gestalt ; das Ganze bildet eine zusammen- 

 hangende Reihe, die man am besten mit dem technischen Aus- 

 drucke ' Formenreihe ' belegen konnte." " Gewohnlich sind 

 die Unterscliiede zwischen den einzelnen Mutationen um so 

 minutioser, je inniger verbunden die Schichten erscheinen, 

 denen die Stiicke entstammen."* 



That variations are often discontinuous may be freely 

 granted, without at the same time admitting such discontinuity 

 to be a frequent characteristic of phyletic history. On the 

 other hand, such a case as the transformation of the Texan 

 species of Satumia, when taken to Switzerland and reared on 

 a new food-plant, into what might almost be called a new 

 species, is a remarkable instance of the possibilities of abrupt 

 change (Moritz Wagner, Die Entsteh. d. Arten, etc., Basel, 

 1889, pp. 307-310). Though the results of palaeontology are 

 too few to prove a negative, they strongly suggest the advisa- 

 bility of caution and reserve upon this point. 



II. The second class of Bateson's results refers particularly 

 to homologies. As these require somewhat extended consider- 

 ation it will be most convenient to allow the author to state 

 his case as fully as the limits of these brief notes will admit. 

 " Thus to compare the members of a series [i. e. of repeated parts 

 or organs] containing different members it is first assumed that 

 the series consisted ancestrally of some maximum number, 

 from which the formula characteristic of each descendant has 



been derived by successive diminutions If it is true 



that each member of a series has in every form an individual 

 and proper history, it follows that if we had before us the 

 whole line of ancestors from which the form has sprung, we 

 should then be able to see the history of each member in the 

 body of each of its progenitors. In such a series the rise of an 

 individual member and the decline of another should then be 

 manifested" (pp. 31-32). Our author then proceeds to give 

 large numbers of cases of variations in the number and char- 

 acter of the vertebrae and ribs, of the teeth, of the digits, and 

 of the carpal and tarsal elements, which he believes to confirm 

 the view of homology formulated above. The consideration 

 of the vertebrae and ribs will be omitted here, because the 

 palasontological evidence as to these organs is too scanty to be 

 available, the number of altogether complete skeletons of 

 fossil mammals which have been found, being of course very 

 limited. 



With regard to the teeth Bateson arrives at the following 

 conclusions : (1) Domestication is not a factor in causing fre- 

 quency of variation. (2) Dental variation may be symmetrical 



* W. Waagen, Die Formenreihe des Ammonites subradiatus. Benecke's 

 Geognost.-Palseontol. Beitrage Bd. II, pp. 179-256. 



