328 
forms by tracing them continuously from zone to zone, and by a comparison 
of the morphological characters of the adults. The group studied by 
Greene is that of Chonetes granulifer, from the Upper Carboniferous rocks 
of Kansas. Here the forms frem 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 Chonetes from 
the Devonian. Chonetes 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 Dielasma and Zygospira.' 
Trilobita.—Studies of the early stages of the development of trilo- 
bites have been published by Barrande (3, 4), Walcott (59, 60, 61), Beecher 
(8S, 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 on “Larval Stages of Trilo- 
bites” (8), and a “Natural 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 
1For additional examples of recapitulation among the brachiopods see the 
following: Beecher, C. E., Studies in Evolution (a series of collected papers), 
Scribners, 1901. Zeecher, C. E., and Clarke, J. M., The Development of some 
Silurian Brachiopoda, Mem. N. Y. 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, 1895. Cumings, E. R., The 
morphogenesis of Platystrophia; A study of the Evolution of a Paleozoic Brach- 
iopod, Am. Jour. Sci., vol. xv, 1905. Raymond, P. E., The developmental change 
in 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. Cotteswold Nat. Field Club, vol. xii, 1901. 
