NATURAL HISTORY OF AMERICAN LOBSTER. 29 1 



immediately in the cytoplasm, and henceforth the growth of the egg is determined by 

 additions to the store of yolk, the materials for the manufacture of which are supplied 

 by the blood. At an early stage the eggs probably multiply by division, and where 

 they do not immediately break away from the parent epithelium they become elongated 

 by mutual pressure, so that their long axes are parallel to each other and perpendicular 

 to the basement membrane. Irruptions of ova, however, always occur at certain points, 

 so that the young eggs appear in bunches along the crests of the original folds. 



The nuclei of those cells destined to form a part of the follicle are easily distinguished 

 by their smaller size, rod-like form, and by the relation to the young eggs which they 

 promptly assume. The nucleus or germinal vesicle grows apace and continues to 

 expand until, at the close of the first year after a given ovulation, it attains a diameter 

 of one-eleventh millimeter. Rarely two or more nucleoli are developed in the young 

 eggs; there is usually but one nucleolus and this of large size. 



When sections of the ovary are examined, after treatment with the usual killing, 

 fixing, and staining fluids, we find the nucleoli of all the eggs lying against the nuclear 

 wall in the same relative positions; that is, at the "bottom" of the nuclei or on the side 

 which was lowest at the time of fixation. The nucleolus is apparently released from 

 its suspension in the nuclear reticulum by the action of the fixative employed, and 

 responding promptly to the influence of gravity, drops like a shot in a bag. The ulti- 

 mate position of the nucleolus is thus solely determined by the direction of gravity, 

 and in reference to the egg itself by the position of the tissue at the time of fixation. 



The growth of the first generation of eggs is exceedingly slow, occupying from four 

 to five or more years, during which the ova must derive their nourishment indirectly 

 from the blood. Swarms of new cells which continue to arise along the axial folds 

 tend to drive the largest and oldest eggs toward the outer walls, a condition which is 

 maintained until these ova approach maturity. When the limit of growth is reached 

 the eggs are dehisced from their capsules, fill the lumen of the ovarian tube, and crowd 

 the germinal folds and younger eggs of the next generation farther and farther toward 

 the periphery. 



We have already referred to the variable color of the organs during this period of 

 their growth. Bright yellow, flesh and salmon color, light olive green, with many inter- 

 mediate tints, are commonly noticed, while after the first eggs are produced, uniformity 

 in the color of the organs prevails. With rare exceptions, after the first egg laying the 

 ovary in due time assumes a characteristic light pea-green color and becomes progres- 

 sively darker with age until maturity is reached. 



CYCLICAL CHANGES IN OVARY AFTER THE FIRST SEXUAL PERIOD. 



We have finally to consider the changes which the ovary normally undergoes during 

 each successive reproductive period. After the eggs are laid the collapsed organs assume 

 a grayish-white tint and appear flecked with green spots — the residual ova which fail 

 of emission and stick fast in the lobes and ducts. In the course of 36 hours or less the 

 ovaries are again solid masses with central germogenal folds, the larger eggs lying nearer 

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