192:2] Phases ix the Development of Chrysemys Cinerea 73 

 expla^•attox of plates 2-4 



Figs. 1, 3-6, Chrysemys picta after Agassiz. 

 Fig. 2, Chrysemys marginata after Agassiz. 



Fig. 7, Chrysemys picta after Gadow. 



Fig. 8, Chrysemys picta after Ditmars. Photographs by permission. 



Fig. 9, Chrysemys marginata after Ditmars. Pliotographs by permission. 



?ig. 10, PTiotograph of C. cinerea. Uterine egg retained for 30 days. Incu- 



bated 48 days. 

 Fig. 11, Photograph of C. cinerea. Incubated 43 days out-of-doors. 



Fig. 12, Photograph of C. cinerea. Incubated 47 days indoors. 



Fig. 13, Photograph of C. cinerea. Laid egg incubated for 45 days. 



Fig. 14, C. picta Hermann, after Schoepff. 



Fig. 15, Plastron of C. bellii after Euthven. 



Fig. 16, Plastron of C. cinerea after Euthven. 



Figs. 17-24, Drawings of plastrons of various specimens showing gradations of 



plastron markings between these figured in 15-16. 

 Figs. 25-26, Drawings of plastrons of two specimens from the same clutch. 

 Fig. 27, Blastopore stage of C. cinerea. Egg retained 30 days. 



Fig. 28, Transverse section showing invagination of C. cinerea. 



Fig. 29, Sagital section of a later stage showing ectodermal cells posterior to 



blastopore. 

 Fig. 30, Blastopore stage typical of C. cinerea. 



Figs. 31, 32, 35, 36, Yolk plug of Chelydra serpentina. 



Fig. 33, Early flexure stage. Egg opened upon removal from oviduct. 



Fig. 34, Outline drawing of embryo of C. cinerea. Uterine egg incubated 20 



days. 

 Fig, 37, Outline drawing of C. cinerea embryo. Laid egg incubated 17 days. 



Fig. 38, Outline drawing of C. cinerea embryo. Uterine egg incubated 28 



days. 

 Fig. 39, Outline drawing of C. cinerea embryo. Uterine egg incubated 30 



days. 

 Figs. 10-13, slightly reduced; 15-24 reduced Vn; 25-26x21^; 27x12; 28-29x50; 



30x20; 31, 32x50; 33x8; 34x4; 35, 36x50; 37x6; 38x5; 



39x3. 



