512 SLOUDIES FOR STUDENTS 
The best example of correlation of ontogenetic stages with 
phylogeny is the genealogy of Medticottia, worked out by Kar- 
pinsky,* who has shown that the Carboniferous genus Pronorites 
goes through the following stages: latisellate protoconch, phyl- 
embryonic; with the second suture it reaches the Anarcestes 
stage, nepionic; about the end of the first revolution the 
lbergiceras stage begins, paranepionic; second revolution shows 
the Paraprolecanites stage, neanic; on the third whorl begins the 
Pronorites stage, adult. Thus with regard to Pronorites the genus 
Anarcestes is phylonepionic, /éergiceras is phyloparanepionic, 
Paraprolecanites is phyloneanic. In the same work Karpinsky 
has shown that Medlicotta is a direct descendant of Pronorites 
and in its development goes through all the stages of the ances- 
tral genus and adds several more. The first revolution of Wedh- 
cottia could not be studied, but on the second revolution was 
seen the /éergiceras stage, metanepionic; on the third whorl the 
Paraprolecanites stage, paranepionic; at the end of the third whorl 
the Pronorites stage, beginning of the neanic; on the fourth whorl 
the Szcanites stage, end of the neanic: on the the fifth whorl the 
Promedlicottia stage, anephebic; and lastly, at end of the fifth 
whorl, Medticottia, adult in characteristics, though not yet in size. 
PALASONTOGENY. 
Groups available.—Vertebrates are out of the question for 
this sort of work, being too highly accelerated in their develop- 
ment; the stages that might be useful in phylogeny are gone 
through before the animal is capable of being preserved as a 
fossil. Inthe Ce@lenterata the relations between Cenozoic and 
Paleozoic forms are not understood, and the ontogeny of avail- 
able forms does not show stages that are striking enough to tell 
much. In Echinodermata difficulty of preservation of fossil 
forms makes ontogenetic study almost impossible, and recent 
forms have been too little studied for any comparison of stages 
of growth with ancient genera to be possible. 
*Mém. Acad. Impér. Sci., St. Pétersbourg, VII Ser., Tome XXXVII, No. 2. 
‘* Ammoneen der Artinsk-Stufe. ”’ 
