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IOWA ACADEMY OP SCIENCE Vol. XXIV, 1917 
cells shows a condensation due to rapid multiplication of cells 
and to the intrusion of wandering leucocytes. There is thus 
Figure 48. — Loggerhead turtle embryo of about 20 days incubation. a. 
Section showing region of elongating ectodermal cells and condensation of 
mesenchyme, b. A portion of, same region enlarged. 
formed in an embryo of about twenty-four days incubation (fig- 
ure 49) a small elevation on the inner surface of the ectoderm 
Figure 49. — Loggerhead 
Beginning of musk gland. 
turtle embryo of about 24 days’ incubation. 1. 
2. Muscle.. 3. Lung. 4. Liver. 
which grows upward, rodlike, through the mesenchyme of the 
carapace (figure 50). After passing through this denser tissue 
Figure 50. — Loggerhead turtle embryo of about 25 days’ incubation. 1. 
Developing gland. 2. Muscle. 3. Muscles of anterior limb girdle. 4. Car- 
tilage of anterior limb girdle. 
of the carapace this rod of cells penetrates the peripheral portion 
of the deeper breast muscles of this region and divides into sev- 
