Bancroft. — Distaplia occidentalis. 



PLATE 5. 



Fig. 30. Periphery of an old ovum and its follicle. 



Fig. 31. Periphery and follicular envelope of an ovum that has just reached the 



pouch. 

 Fig. 32. Ectoderm and test at an early stage in the formation of the test. 

 Fig. 33. Section of the test when a little more developed. 

 Fig. 34. Test, still farther developed. 

 Figs. 35-46. Various stages in the degeneration of the test cells of Styela mon- 



tereyensis. 

 Fig. 35. Ovum containing the test cell is 84 X 65 fi. Test cell shows vacuoles 



and intravacuolar bodies. 

 Fig. 36. Ovum 92 X 69 p. 

 Fig. 37. Ovum 108X69^. 

 Fig. 38. Test cell from the same ovum. 

 Figs. 39, 40. Test cells, from another ovum, showing the formation of the central 



corpuscle within the intravacuolar bodies. 

 Fig. 41. OvumgexSO.u. 



Figs. 42, 43. From an ovum measuring 134 X 111 yu. 

 Fig. 44. Ovum 92 X 76 fi. 

 Fig. 45. Ovum 169 X 80^. 

 Fig. 46. Ovum, nearly mature, measuring 108 X 92 /u. 



