246 BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Fig. 136. Ovary immediately after egg laying, seen from below. From lobster No. 52, table 20. The 
oviducts are filled with unextruded eggs; a few of these ova are also seen in the ovaries. 
Immature eggs from this ovary are shown in fig. 134. The yellow flecks are the remains 
of unextruded eggs of a former egg generation; that is, they have been in the ovary two 
years at least. Drawn in natural size and color from life. July 28, 1891. 
Fig. 137. Ovary of lobster No. 87, table 20, bearing external eggs. The latter have been laid about 
six weeks (date of laying about July 10). The ovarian eggs possess a dark-green core and 
lighter periphery. At the period of ovulation they are colorless, as shown in figs. 134 
and 136. August 21, 1891. Drawn in natural size from life. 
Fig. 138. Ovary of female which has recently hatched a brood. Taken July 30, 1891. For description 
of lobster see No. 95, table 20. The pea-green color is characteristic of the ovary at this 
time. The contained eggs, one of which is shown in fig. 133, are approximately one year 
old. The difference in relative size between the ova shown in figs. 133 and 134 thus 
represents a year’s growth, while the relative difference in size between the ova shown in 
figs. 134 and 135 represents only six weeks of summer growth. 
We thus see that a generation of ovarian ova grow very rapidly during the first sum- 
mer following the last ovulation. They then enter upon a period of quiescence, growing 
but slowly, like the external embryos during the succeeding winter. The second summer 
following ovulation is marked by a second period of rapid growth, followed in turn by a 
second period of quiescence during the succeeding winter. At the beginning of the third 
summer after ovulation this generation of eggs is ready for extrusion. That the spawn- 
ing periods are thus two years apart is a valid inference drawn from the study of the 
anatomy of the reproductive organs. Yellow spots mark as before the remains of degen- 
erate eggs which failed of emission at the last reproductive period. The characteristic 
condition of the ovary shown in this drawing proves that annual breeding is an 
impossibility. Drawn in natural size and color from life. 
Plate 39. 
Fig. 139. Part of transverse section of ovary of lobster, No. 52, table 20, with external eggs in early 
segmentation, the ova having been laid about thirty-six hours. The peculiar glandular 
organs are now seen in the peripheral parts of the lobes. O. G., ovarian gland; O. TV., 
wall of ovary. 36 times natural size. 
Fig. 140. Part of transverse section of ovary of lobster No. 94, table 20. Glands absent; ovaries 
approaching maturity. 36 times natural size. 
Fig. 141. Part of transverse section of nearly ripe ovary, from lobster No. 75, table 20. August 19, 1890. 
The nucleus or germinal vesicle is shown in one of the nearly ripe eggs. (For more 
detailed drawing of nucleus, see fig. 160.) Bl. S., blood sinus; Ct, nodule of connective 
tissue. O. G., ovarian gland 22 times natural size. 
Fig. 142. Part of transverse section of ovary of lobster No. 52, table 20, showing follicle cells which 
have wandered into the egg and are undergoing degeneration. Dg, vesiculated masses of 
chromatin, the fragments of degenerated cells; Bl. S., blood sinus containing blood 
cells. 457 times natural size. 
Fig. 143. Part of transverse section of ovary, the same as in fig. 141, showing the gland-like organs. 
Bl. S., blood sinus (dotted line should be continued across gland). 211 times natural size. 
Plate 40. 
Fig. 144. Right pleopod of adult female lobster, seen from posterior surface. Drawn from alcoholic 
preparation, with camera and dissecting microscope, the cuticle being removed from one 
side to show distribution of cement glands in swimmerets. 4 times natural size. 
Fig. 145. Fold of glandular epithelium from transverse section of ovary of lobster No. 75, table 20. 
From same as fig. 141. ys, body resembling yolk spherule. 190 times natural size. 
Fig. 146. Transverse section of lobe of ovary shown in fig. 131, plate 38. From No. 2, table 32. 67 
times natural size. 
Fig. 147. Part of transverse section of ovarian lobe from a lobster with external eggs near the point 
of hatching. The condition of this ovary closely corresponds to that shown in fig. 138. 
June 30, 1890. Bl. S., blood sinus. 36 times natural size. 
