THE AMERICAN LOBSTER. 247 
Rig. 148. Part of transverse section of ovary of lobster No. 51, table 20, showing the inner or primary 
egg membrane (shaded dark), and the follicular epithelium by -which it is secreted. HI. S., 
blood sinus. 211 times natural size. 
Fig. 149. Part 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). 540 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 
be detected in this egg. (See figs. 139 and 149.) B. M., 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 
3 ! 3 mm., of nucleus mm. 353 times natural size. 
Fig. 155. Young ovum from same ovary as the last. Diameter of egg -fa 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 y'j- mm., of nucleus ^ nun. 353 times natural size. 
Fig. 157. Young ovum from same ovary as the last. Diameter of egg a little over mm., of nucleus 
- r V 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 - 1 7 , ) - mm., of nucleus -jV 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-J- mm., of nucleus -fa 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 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 -fa 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 Woods 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. Oa 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. 
