310 EXPLANATION OF THE PLATES. 



Plate 19. 



Development of cephalopoda (Sepia offlcinalis). Keferstein, 

 1. c, t. 123. Explanation of reference letters and 

 fig-ures : D. Outer yolk sack. o. Mouth, m h. Buccal 

 mass. V. Stomach, h r. Branchiae, h i. Ink-bag. 

 c h. Shell. J. Siphon, m c. Musculus collaris. c h. 

 Button cartilage, n c h. Neck plate. G' G" . Under 

 and upper head flaps, o c. Eyes. 1, 2, 3, 4, 5. Arms. 



18, Three stages of the "foldings" of Kolliker, prior to 



oviposition, ........ 127 



19. An egg, somewhat magnified, ..... 127 

 20-22. Eggs showing stages of segmentation, . . 12Y 

 23, 24. Eggs with the capsules cut open, showing the 



embryos, . . . . . . . .127 



25-30. Progressive stages of segmentation, . . .127 

 31, 32. Front and side view of Kolliker 's fourth stage of 



development, . .127 



33. Embryo in sixth stage, . . . . . .127 



34-36. Embryo in seventh stage, ..... 127 



37. Embryo in eighth stage, from the back, . . . 127 



38. Section of an advanced embryo. 1 represents the 



cephalic and 3 the abdominal portion of the inner 

 yolk-sack, . . . . . . . .127 



Plate 20. 



39. Embryo of Sepia offlcinalis, three or four times smaller 



than its yolk-sack. (Kolliker, Entwicklungsgeschichte 

 der Cephalopoden, t. 4, f. 38), . • . . 127 



40. Side view of the same. J", siphon, .... 127 



41. Dorsal view of a more developed embryo, oc, eyes; 



D, yolk sack, 127 



42. A young Sepia officinalis, ventral view, the mantle cut 



open. i^Cuvier, Nouv. Ann. du Mus ) o. Mouth. T. 

 Tentacles. J. Siphon, c h. Button-like cartilage. 

 b r. Branchige. h i. Ink-bag. 1 to 5. Arms, . 127 



43. Embryo of Purpura lapillus, Linn. (After Koren and 



Danielssen.) o e, oesophagus ; c h, shell ; P, foot ; y, 

 ganglia , o t^ otolite ; s, salivary gland, . . . 127 



44. Macgillivraya pelagica. (After Macdonald), . 127, 130 



45. Larva of Eolis. (After Alder and Hancock.) o, oper- 



culum. The larva is not larger than the letter o, 127, 137 

 49. Dentition of Macgillivraya pelagica. (After Mac- 

 donald), 127, 130 



47. Sinusigera cancellata, Orb. (After H. and A. Adams' 



Genera), ........ 127, 130 



