549 
This work on Chrysemys marginata was first done in 1910—1911 
but its publication has been delayed, and in the meantime BENDER!) 
has made a detailed study of the mandibular and hyoid arches, and 
the tympanic cavity in Testudo graeca. He regards the entire colu- 
mella as a product of the hyoid arch, although he does not consider 
the extra-columella a primary element of it. 
Thus it is seen that the few who have investigated the develop- 
ment of the Chelonian columella have obtained contradictory results, 
and it still remains to be decided which of the three possible origins 
of the columella is correct (pure hyoid, pure capsular, or a combination 
of the two). 
Materials and Methods. 
While the common painted turtle, Chrysemys marginata, a 
species of the family Emydae, has been used as a basis for this study, 
the musk turtle, Aromochelys, has also been studied in several stages 
and found so similar to Chrysemys marginata that no separate de- 
scription is given. 
In all, ninteen series of Chrysemys marginata, ranging from em- 
bryos of 6 mm. total body length to young adults of 26 mm. cara- 
pace measurement, have been examined, and two models have been 
prepared. All measurements were made after fixation. Where total 
body measurements were necessary, they were not taken along the 
curved axis but in a straight lme between the points of greatest 
convexity. Upon examination of the series method was found inac- 
curate, for in a few instances embryos of lesser measurement proved 
slightly older than those of greater length. The variability of cur- 
vature in individuals is undoubtedly the cause for this discrepancy, 
but it is not great enough to have made more than one or two milli- 
meters difference in the measurements. 
ZENKER'S fluid was the fixer used. The youngest embryos 
were stained in toto with borax- or para-carmine, and embedded and 
cut in paraffin. In the somewhat older specimens the in toto stain 
was disregarded, and DELAFIELD’s Hematoxylin and Orange G were 
1) BENDER, O. 1911. Über Herkunft und Entwickelung der Columella auris 
Fei Testudo graeca. Anat. Anz.; 40, pp. 161—177. 
BENDER, O. 1912. Uber die Entwickelung des Viszeralskeletes bei Testudo 
yraeca, Abhandl. d. k. Bayerischen Akad. d. Wiss.; 25, pp. 1—62. 
