'THE AMERICAN LOBSTER. 247 



Fig. 148. Part of transverse section of ovary of lobster No. 51, table 20, showing the inner or primary 

 egg membrane (shaded dark), and tlio follicular epithelium by which it is secreted. HI. S., 

 blood .sinus. 211 times natural size. 



Fig. 149. Fart of transverse section of ovary of lobster No. 52, table 20, showing part of an egg and 

 follicular cells in contact with it. Those which have wandered into the yolk after- 

 wards degenerate. The external eggs borne by this lobster were in an early stage of 

 segmentation. /. c, follicle cells immersed in the yolk. 211 times natural size. 



Plate 41. 



Fig. 150. Degenerating cells from the ovary of lobster No. 76, table 20. The larger body to the left is 

 the remains of what was once a mature egg, which having failed of emission at the time 

 of egg-laying has suffered degeneration. The tough egg membrane seems to defy com- 

 plete absorption. To the unaided eye such an egg appears as a yellow fleck, if visible at 

 all (see fig. 136). 510 times natural size. 



Fig. 151. Part of horizontal section of ovary from lobster No. 76, table 20, showing ova inclosed in 

 folds of follicular epithelium. This ovary was slit open along the mid-dorsal line, pinned 

 out, hardened, and sectioned in longitudinal, horizontal planes. 67 times natural size. 



Fig. 152. Part of transverse section of ovary of lobster No. 52, table 20, showing the developing ovum 

 and its relation to the folds of glandular epithelium. Remnants of degenerating cells can 

 bedetectedin this egg. (See figs. 139 and 149.) B. H., basement membrane; Bl. S., blood 

 sinus; G. E., glandular epithelium. 281 times natural size. 



Fig. 153. Glandular epithelium from transverse section of ovary of lobster No. 75, table 20. F. G., 

 vacuoles, probably representing fatty globules which have been removed in the process of 

 preparing the tissue for sectioning ; ys, bodies resembling yolk spherule. 253 times natural 

 size. 



Plate 42. 



Fig. 154. Ovum in early stage of growth, from ovary of lobster No. 52, table 20. Diameter of egg 

 Jj mm., of nucleus -^ mm. 353 times natural size. 



Fig. 155. Young ovum from same ovary as the last. Diameter of egg tV mm., of nucleus ■£$ mm. 353 

 times natural size. 



Fig. 156. Young ovum from same ovary as the last. This nucleus contains two nucleoli. Diameter 

 of egg -^ mm., of nucleus t> 1 4 - mm. 353 times natural size. 



Fig. 157. Young ovum from same ovary as the last. Diameter of egg a little over -^ mm., of nucleus 

 iV mm. 353 times natural size. 



Fig. 158. Nucleus of ovum from transverse section of ovary of lobster with external eggs about to 

 hatch. From same as fig. 147. Diameter of egg ^ mm., of nucleus ^ mm. 353 times 

 natural size. 



Fig. 159. Nucleus of ovum from nearly ripe ovary of lobster No. 94, table 20. See fig. 140 for ovarian 

 section. Diameter of egg 1^ mm., of nucleus tV mm. 353 times natural size. 



Fig. 160. Nucleus of ovum from ovary of lobster No. 75, table 20. For ovarian section and position 

 of nucleus, see fig. 141. Ovary ripe. Diameter of egg If mm., of nucleus -fa mm. 353 

 times natural size. 



Fig. 161. Nucleus of egg in process of emitting polar cells. From section of unextruded egg taken 

 from the oviduct. Diameter of egg 1.31 mm., of nucleus -^ mm. The nucleus is in process 

 of karyokinesis and lies close to the surface of the egg. The axis of the nuclear spindle 

 appears somewhat oblique to the surface. July 28, 1891. 353 times natural size. 



Fig. 162. Bifurcated rostrum of lobster taken at AVoods Hole, Massachusetts. Dorsal view. Two- 

 thirds natural size. 



Fig. 163. Profile view of the same. Two-thirds natural size. 



Fig. 164. Ovaries of lobster, from below, showing bifurcation in left anterior lobe. Ovary light golden- 

 yellow color. Ova very immature. May 19, 1892. Two-thirds natural size. 



Fig. 165. Part of gastrolith, separated into its constituent spicules, taken fresh from the wall of the 

 stomach of a lobster nearly ready to molt. For chemical analysis, see No. 0a of table, 

 Appendix II. Compare cut 8, plate C. The broad flattened spicule at the lower right- 

 hand corner of the drawing is from the peripheral convex margin of the gastrolith. 5.3 

 times natural size. 



