100 HYATT ON THE TERTIARY vSPECIES 



APPENDIX I. 



On page 27 I have written, that I wondered no authors except Prof. Cope and myself 

 had made the law of acceleration an object of investigation. 



This statement is not wholly correct, since I find in a work just received, " Studien liber 

 die Stammes-geschichte der Ammoniten," by Leopold Wiirtenberger (Leipzig, Ernest 

 Gunther, 1880, 8vo., pp. 110, with four Stamrntafeln), that the author has used this 

 law of heredity, though evidently misunderstanding its fundamental character, as one of 

 the laws of heredity, and explaining it as the result of the action of the law of natural 

 selection. It becomes interesting, also, to observe how closely his statements and facts 

 agree with those previously made in my publications ; for example, on page 28, he writes 

 as follows : " Wenn niimlich eine Veninderung welche fiir die gauze Gruppe eine wesent- 

 liche Bedeutung erlangt, zuni erstenmal auftritt, so ist dieselbe nur auf einem Theil des 

 letzten Umganges angedeutet. Gegen jungere Ablagerungen hin tritt diese Veranderung 

 immer deutlicher hervor und schreitet dann, dem spiralen Verlaufe der Schale folgend, 

 nach und nach immer weiter gegen das Centrum der Ammonitenscheibe fort ; d. h. ,sie 

 ergreift allmahlich immer mehr audi die inneren Windungen, je h(iher man die betref- 

 fende Form in jungere Schichten hinauf verfolgt." 



" When, for instance, a variation which attains a substantial importance for the whole 

 group, makes its appearance for tlie first time, it is exhibited only upon a part of the last 

 (outer) whorl. This variation comes out ever more distinctly as the strata are younger, 

 and advances, following the spiral trend of the shell, step by step, towards the centre of 

 the spiral : that is to say, they (the characteristics) strike gradually more and more 

 towards the inner whorls, as one follows the forms from the older into the younger (later 

 formed) beds." 



This statement is an exact transcript of what I have repeatedly written in various 

 essays upon the Ammonites, and also gives the fundamental fiicts upon which all my inves- 

 tigations have been based for fourteen years. 



Compare the above, for example, with the following sentences from p. 203, of my 

 memoir in Vol. 1st of the Memoirs of Bost. Soc. Nat. Hist., read Feb. 21, 1866, and pub- 

 lished in 1867. 



" The young of higher species are thus constantly accelerating their development, and 

 reducing to a more and more embryonic condition, (or entirely passing over) the stages 

 of growth corresponding to the adult periods of j^'i'c-exisilmj or lower species." 



" In other words, there is an unceasing concentration of the adult characteristics of lower 

 species in the young (or inner whorls) of higher species, and a consequent displacement 

 of other embryonic features (in these inner whorls), which had themselves, also, ^orevioicsly 

 helonrjed to the adidt jJeriods of still lower forms ." 



With reference to the characters of the Ammonitoid shells, on p. 94, he says : " dass die 

 Vevanderungen an den Sculpturen, sowie an den iibrigen Charakteren der Ammoniten- 

 schalen sich zuerst auf dem letzten (ausseru) Umgange derselben bemerklich machen, vmd 

 dass dann eine solche Veranderung bei den nachfolgenden Generationen sich nach und 

 nach immer weiter gegen den Anfiing des spiralen Gehiiuses fortschiebt, bis sie den gross- 

 ten Theil der Windungen beherrscht." 



