328 



forms by tracing theui continuously from zone to zone, and by a comparison 

 of the morphological characters of the adults. The group studied by 

 Greene is that of Ghonetes grain/lifer, from the Upper Carboniferous rocks 

 of Kansas. Here the forms from the higher zones repeat in their onto- 

 geny the characters of forms from the lower zones with great fidelity. The 

 very young stages also recall very forcibly the species of Ghonetes from 

 the Devonian. Ghonetes granulifer is also very interesting from the fact 

 that the first hinge-spines appear very much earlier in the ontogeny than 

 is the case in the Devonian species studied by Raymond (46). therefore 

 showing a considerable degree of acceleration of this character during 

 the interval from the Devonian to the Upper "Carboniferous. 



Other interesting cases of recapitulation among brachiopods have 

 been pointed out by Beecher and Schuchert (12) in the development of 

 the brachial apparatus in DieJasma and Zygospira. 1 



Trilooita. — Studies of the early stages of the development of trilo- 

 bites have been published by Barrande (3, 4), Walcott (59, 60, 61), Beecher 

 (8, 9). Matthew (39. 40. 41) and others, but for indication of the corre- 

 lation of the ontogeny and the phylogeny in this class we are almost en- 

 tirely indebted to Beecher. In his papers oh "Larval Stages of Trilo- 

 bites" (8), and a "Xatural Classification of the Trilobites" (9), he has 

 not only pointed out the remarkable way in which characters are re- 

 capitulated in this class, but has also proposed what is probably to be re- 

 garded as the most perfect example of a phylogenetic classification of a 

 group of organisms, in existence. 



The earliest developmental stage of trilobites that has ever been found 

 (barring supposed trilobite eggs) is the larval stage or "protaspis," as it 

 is called by Beecher (8). The protaspis is a minute body of ovate or dis- 

 coid shape, and about a millimeter in length. This larval stage has 



1 For additional examples of recapitulation among the brachiopods see the 

 following: Beecher, C. E., Studies in Evolution (a series of collected papers), 

 Scribners, 1901. Beecher, C. E., and Clarke, J. M., The Development of some 



Silurian Brachiopoda, Mem. N. T. State Mus., No. I, 1889. Beecher, C. E.', and 



Schuchert, C, Development of the shell and brachial supports in Dielasma and 

 Zygospira, Proc. Biol. Soc. Washington, vol. viii, 1S93. Cumings, E. R., The 



morphogenesis of Platystrophia ; A study of the Evolution of a Paleozoic Brach- 

 iopod. Am. Jour. Sci., vol. xv, 1903. Raymond. P. E.. The developmental change 



i'n some common Devonian brachiopods. Am. Jour. Sci., vol. xvii, 1904. Greene, 

 F. C, The development of the Carboniferous brachiopod Chonetes granulifer, Owen. 

 Jour. Geol., vol. xvi, 1908. Buckman, S. S., Homeomorphy among Jurassic 



Brachiopoda. Proc. Gottesicold Nat. Field Club, vol. xii, 1901. 



