432 



On the other hand in Coroniceras trigonatum, Hyatt', 

 which is an individual of a retrogressive evolutionary series, the follow- 

 ing auxologic changes may be noted : 



f Brephic , Neanic, Ephebic, Gerontici __ , i .-. 



{ r^ . ' \n. , , o .if- Here also the Gerontic stage 



I Spinous, Costate, Costate, femootn I 



is Catabatic ; but it is a reversion to a stage of phylogenetic develop- 

 ment omitted from the ontogeny on account of earlier inheritance. 

 The same applies to the ornamentation of both the Neanic and Ephe- 

 bic stages. 



Phylogenetic stages. 

 It must be kept in mind that the terms hitherto considered denote 

 stages in the growth of an individual. They or their predecessors have, 

 however, often been applied, even by Hyatt himself, to stages in the 

 history of a race. Beecher, though he points out the difference in 

 clear enough language (op. cit. H, p. 148), nevertheless speaks of 

 Gwynia and Cistella as Nostologic (= Hypostrophic) types of Tere- 

 bratuloids ; by which he means that in their Ephebic stage they 

 resemble the earlier stages in the history of the group, or the Brephic 

 stages in the ontogeny of such a form as Terebratulina. This use 

 of the same words for two very distinct ideas leads either to confusion 

 of thought, or to the employment of cumbrous qualifying phrases. We 

 therefore suggest that , when it is desired to express stages of phylo- 

 geny, the syllable phyl- should be prefixed to the above terms, as 

 shown in the annexed table. In this table we also give, in the first 

 column, the physiological terms employed by Hseckel for Growth, 

 Perfection, and Decline in Ontogeny ; and , in the last column, the 

 terms used by the same writer to denote corresponding periods in 

 Phylogeny. It should be noted that these latter terms are not Mor- 

 phological, but have reference chiefly to number of species and indi- 

 viduals, and partly also to size and predominance. They have of late 

 been used, it seems to us wrongly, in a morphological sense, especially 

 by American writers, probably for want of the very terms we now pro- 

 pose. Beecher, for instance, in his most interesting essay on the de- 

 velopment of Bilobites (= Orthis biloba and allies), speaks of 

 certain forms as Epacmic and others as Paracmic , when it would pro- 

 pably be more in accordance with his meaning to call them Phylo- 

 brephic and Phylogerontic. Thus also we should say that the Produc- 

 tidae attained their Paracme in the Permian , when they were repre- 

 sented by the Phylogerontic Strophalosia and Aulosteges; that 

 the characters of the Neanic and Ephebic stages of Coroniceras 



7 Genesis of Arietidae. PI. VI fig. 3. PI. VII fig. 1. p. 182. 



