42 GENESIS OF THE ARIETID. 
among the Ammonites. This author, in his “Studien tiber die Stammesgeschichte 
der Ammoniten,” ! traces the Armatus or Aspidoceras stock of the Upper Jura to 
the Planulati; that is, to the genera Coeloceras and Dactylioceras, which last I 
had previously described and traced to an origin in Deroceras Dudressiert of the 
the Lower Lias2 His work is a summary of evidently extensive observations 
upon the Ammonites of the Upper Jura, all of which he traces directly or indi- 
directly to the Planulati. Whether he can sustain this opinion will be questioned 
by some until he has published his plates. He has, however, studied the series 
according to proper methods of analysis, and should be given the credit of the 
doubt. We also, though the author fails to notice the fact, have traced Pelloceras 
athleta to the same species in the Lias, Amm. annulatus Quenst., and published the 
remark ® that they were genetically connected by intermediate forms. Our obser- 
vations, therefore, closely accord upon this very important species, and we also 
agree in the view that most of the jurassic genera we have included in the 
Spinifera and Plicatifera can be traced to Ca/. Pettos as the probable radical.* 
In his fourth chapter Wiirtenberger gives the history of the evolution of the 
Lallierianus series, in which he traces degeneration in the lobes and saddles, 
showing that changes of all kinds appear first on the outer (adult or senile) whorl 
of the ancestral forms, and encroach more and more on the inner (younger) 
whorls in descendants. Neumayr® considers that Wiirtenberger was the dis- 
coverer of the law of acceleration in development, and this author states that he 
first published his new discoveries in “ Ausland ” of 1873,— about five years 
after the appearance of precisely similar statements in such scientific periodicals 
as the Proceedings of the Philadelphia Academy, by Professor Cope, and the 
Proceedings and Memoirs of the Boston Society of Natural History,” by the 
author. Professor Cope has lately republished his discoveries in a volume en- 
titled “ The Origin of the Fittest,” and in these masterly essays those who are 
interested may get a full view of his mode of explaining this law, and will find 
very complete series of illustrations of the character and meaning of parallel 
series and other related phenomena. 
The decision as to who discovered the law of acceleration is only historically 
interesting ; but it is of general importance that so many persons agree, and 
that an eminent paleontologist like Neumayr, who has studied such phenomena 
among fossils, considers the law to be true in its application, as tested by him, 
with some exceptions. He does not state the exceptions, however, and they 
cannot be discussed. The opinions of Wiirtenberger and Neumayr that some 
species inherited characteristics at later stages than those in which they occurred 
in any ancestral species or pair, seem at present to rest upon the insecure basis 
of the apparent need of this assumption in order to account for acceleration as 
1 Ernst Gunther, Leipzig, Darwinistische Schriften, No. 5. 
2 Non-reversionary Series of the Liparoceratide, etc., Proc. Bost. Soc. Nat. Hist., January, 1872, and 
Appendix to the same, with a geological table, Ibid., May 20, 1874. 
8 Proc. Bost. Soc. Nat. Hist., Appendix to Non-reversionary Series of the Liparoceratide, 1874, p. 33. 
4 See above, pp. 23, 24. 
5 Zeitsch. d. deutsch. geo]. Gesellsch., p. 868. 
6 See above, page 28, note 3, and Proc. Bost. Soc. Nat. Hist., 1870, pp. 72, 73. 
