OF PLANOCERA ELLIPTICA. 325 



REFERENCES TO THE FIGURES.* 



Figs. 1 and 2. — Ovarian eggs observed in an individual from the Harbor of Boston, on the 22d of Decem- 

 ber, 1848. 



Figs. 3 and 4. — Ovarian eggs from an individual caught in the Harbor of Beverly, and likewise observed 

 on the 22d of December 1848. Fig. 3 is seen under the same magnifying power as flg. 1 and 2, and 

 represents one of the eggs of fig. 4, which is seen under a low power. 



Figs. 5 and 6. — Eggs before the laying, as observed on the 25th of May, 1849. 



Fig. 7. — A regular band of laid eggs in natural size, a portion of which is seen magnified in a. 



Fig. 8 — 11. — Interrupted and irregular bands of laid eggs in natural size. 



Figs. 12 and 13. — Appearances of the eggs a short time after the laying. Fig. 12 a represents the struc- 

 ture of the yolk under a very high power. 



Fig. 14. — Exceptional case of two yolk spheres within the same egg membrane, observed a short time after 

 the laying. 



Figs. 15 — 43. — Phases in the division of the vitellus. Fig. 17 exhibits three floating cells issuing through 

 an artificial split caused by pressure. In figs. 24 and 38, transparent hernias are seen upon the 

 spheres of division. Fig. 35 a illustrates the structure of the yolk under the same optical power 

 as fig. \1 ah c. 



Figs. 44 and 45. — Mulberry shape of the yolk with floating cells, in fig. 45. Fig. 45 a illustrates the 

 structure of the yolk at that period. 



Fig. 46 — 49. — State of repose of the egg during which the yolk becomes transparent. Floating cells may 

 be seen in fig. 46 and 48, whilst fig. 47 exhibits transparent herniae. 



Figs. 50, 52 and 53. — The embryo, when its motion begins. Numerous floating cells in fig. 52. 



Fig. 51. — Exceptional ca.se of a very small vitellus or yolk, with floating cells. 



Fig. 54. — Structure of the embryonic substance as observed in fig. 53. 



Fig. 55. — The embryonic substance assuming two characters, a central and a peripheric one; ah c, struc- 

 ture of the central portion. 



Fig. 56. — The embryo of fig. 55, more highly magnified, in order to show the vibrillaj. 



Figs. 57 — 74. — Temporary embryonic forms under an abnormal impulse of development, artificially 

 pressed out of the egg membrane. Any of these forms will successively assume the series of shapes 

 here represented. Fig. 69 is a ca-se similar to that in fig. 51, but much further developed, and pro- 

 portionally smaller. 



Figs. 75 — 93. — Normal development of the embryo. Fig. 81, structure of fig. 80. Fig. 82 a represents 

 the structure in fig. 82. In figs. 84 — 93, the membrane of the egg is not represented, it having 

 been purposely brokeu open to allow the embryo to escape. Fig. 82 is seen from below in 86, and 

 from above in fig. 87. Fig. 85 represents, from below, the case where four protuberances are extant, 

 instead of three as represented in fig. 86. Fig. 92 is an upper view of fig. 91. Fig. 93 represents an 

 embryo contracted upon itself. 



Figs. 94 — 98. — Camel-like form of the larva viewed in profile, fig. 94 ; from above, fig. 97 ; from below, 

 fig. 98 ; from behind 95, and in front fig. 96. 



Figs. 99 — 103. — Dromedary-like form of the larvae, viewed in profile fig. 99 ; from above fig. 100 ; from 

 below, fig. 101; from behind fig. 102; and in front, fig. 103. 



Figs. 104 and 105. — The chrysalis; fig. 104, seen from above; fig. 105 transverse section. 



*Most of the figures are drawn under the same magnifying power, with the exception of a few. Tlie figs, in 

 natural size will furnish excellent means of proportional comparisons. 



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