ON DEVELOPMENT OF ATYEPHIRA COMPRESSA. 427 
Fig. 34.— Egg divided into sixty-four parts by the third set of transverse 
furrows. 
Fig. 35. — Egg at the end of the second resting stage, seen by the trans- 
mitted light. A weak acetic acid preparation. 
Figs. 36 and 37. — Two longitudinal sections of an egg of the same stage 
as Fig. 30. 
Fig. 38. — A longitudinal section of an egg divided into sixteen equal 
parts. 
Fig. 39. — A longitudinal section of an egg divided into sixty-four parts. 
Fig. 40. — A longitudinal section of an egg divided into 256 parts. 
Figs. 41 and 42. — Two views of an egg, showing the germinal disk. Im- 
mersed in Kleinenberg’s picro-sulphuric acid for about fifteen minutes. X 65. 
Fig. 43. — A longitudinal section of the germ disk of an egg of the same 
stage as Figs. 41 and 42. Camera b b and 2. 
Fig. 44. — Side view of an egg of the stage slightly later than that repre- 
sented by Fig. 42. X 40. 
Figs. 45, 46, 47, and 48. — Different stages of the gastrula of the egg. 
Front and side views, x 40. 
Figs. 49 and 50. — Gastrula cavity nearly closing. X 40. 
Fig. 51. — A longitudinal section through the gastrula cavity of an egg at 
the same stage as Figs. 45 and 46. Camera b b and 4. 
Fig. 52. — A longitudinal section through the gastrula cavity of the stage 
represented in Figs. 47 and 48, showing the formation of mesoderm cells. 
Camera d d and 2. 
Fig. 53. — A longitudinal section through the gastrula cavity at the stage 
represented in Figs. 49 and 50, showing the closure of the blastopore. 
Camera B b and 4. 
Fig. 54. — A longitudinal section through the region where the gastrula 
cavity has closed. Camera d d and 2. 
Figs. 55 and 56. — Two views of an embryo in which the carapace ( cp .), 
mandibles ( md .), and the cephalic lobes (oc.) have appeared. X 40. 
Figs. 57, 58, and 59. — Three views of an embryo, slightly more developed 
than the last, x 40. 
Fig. 60. — Embryo still more developed, seen from embryonic pole. X 40. 
Fig. 61. — Nauplius stage of an embryo, viewed from embryonic pole. X 40. 
Fig. 62. — A longitudinal section of an embryo represented by Fig. 61. 
Camera D D and 2. 
Figs. 63, 64, 65, and 66. — Three consecutive transverse sections of the 
nauplius, showing the formation of the nervous system. Camera d d and 2. 
Fig. 67. — A transverse section of a nauplius, slightly older than the last. 
Camera d d and 2. 
Fig. 68. — Surface view of an embryo older than Fig. 61. X 150. 
