238 FOOT-NOTES TO EVOLUTION. 
Brachiopoda.—The brachiopods have this decided 
advantage, that they can be hatched in marine labora- 
tories, and the various stages studied from the egg up, 
as has been done by Brooks, Kovalevski, Lacaze-Du- 
thiers, Morse, and Shipley, with the genera Ciste//a, Glot- 
tudia, Lacazella, Liothyrina, and Terebratulina, But it 
was reserved for the paleontologists Beecher, J. M. 
Clarke, and Schuchert to correlate the ontogeny of liv- 
ing forms with ancestral genera, and give a biogenetic 
classification of the Brachiopoda* based on ontogenetic 
study. 
In living specimens the subdivisions of the embryonic 
stage, protembryo, mesembryo, neoembryo, and typem- 
bryo may easily be made out, but since these are shell- 
less the work of the paleontologist begins with the phyl- 
embryonic substage, when the shell gland secretes the 
protegulum. From this upward the paleontologist 
works on equal terms with the zodlogist, for the suc- 
ceeding stages are capable of preservation, and may be 
compared with ancestral genera. Beecher and Schu- 
chert + have demonstrated that the Ancylobranchia (Tere- 
bratuloids) all go through a primitive Centronelliform 
stage, and that the Melicopegmata (spire-bearers) do the 
same, and are for a while genuine Amcylobranchia. Schu- 
chert’s classification of the Brachiopoda, published in 
Eastman’s translation of Zittel’s Text-Book of Paleontol- 
* For correlation of stages of growth with generic changes, 
and for the literature on ontogeny and phylogeny of Brachiopoda, 
see papers by Dr. C. E. Beecher, Amer. Jour. Sci., vol. xliv, Au- 
gust, 1892, Development of Brachiopoda, Part II; and Trans. 
Connecticut Acad. Sci., vol. ix, March, 1893, Revision of the 
Families of Loop-bearing Brachiopoda; and The Development 
of Terebratalia Obsoleta Dall. 
t Proc. Biol. Soc. Washington, vol. viii, July 13, 1893. Devel- 
opment of the Brachial Supports in Dielasma and Zygospira. 
