152 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



of follicular cells, however, screens this particular egg (fig. 152) from the lumen of the 

 glandular fold. In some cases, however, I have seen the glandular cells in direct 

 relation with the yolk, with amoeboid cells passing into the egg along the line of 

 contact (plate 40. fig. 149). At this point cells are sometimes seen completely engulfed 

 in the food yolk. Their nuclei swell to a somewhat larger size, and then speedily 

 degenerate. Faint ghost-like outlines can be detected for some time; then the 

 chromatin becomes concentrated about the walls of a gradually dwindling vesicle 

 (plate 39, fig. 142, Dg.). Finally the chromatin is reduced to very small stainable 

 fragments. In other cases the chromatin probably breaks up more immediately into 

 a swarm of minute particles, which remain in the interstices of the yolk spheres in 

 the peripheral parts of the egg. The "plasmic vesicles" or vacuoles, which Bumpus 

 (30) has described, are products of the cell degeneration just considered. 



Eggs which have been well started on the road of normal growth suddenly go into 

 a decline and are probably finally absorbed into the blood, somewhat as the follicle 

 cells are converted into nutriment within the eggs. (See pp. 211-213.) A number of 

 such degenerating ova are seen to the right of tig. 150, plate 41. They are filled with 

 refractive globules, which are undoubtedly of an albuminous nature. 



After the lapse of from ten to fifteen days after ovulation (the external eggs being 

 then in the egg-nauplius stage), the ovarian glands have almost wholly disappeared. 

 The walls of the follicular folds, now crowded to the extreme periphery beneath the 

 ovarian wall, are shrunken and crumpled. At a still later period (attached eggs with 

 eye pigment, from four to five weeks old) the glands are reduced to shriveled remnants. 

 Later still, no vestige of them is seen. 



STRUCTURE OF THE OVARY AT TIME OF HATCHING OF EXTERNAL EGGS. 



When the external eggs are ready to hatch, the ovarian ova have had nearly a 

 year's growth. The appearance of the ovary at this time is shown in fig. 138, plate 38, 

 and its structure in fig. 147, plate 40. It has a characteristic pea-green color, and the 

 largest peripheral ova (fig. 133, plate 38) have a diameter which is equal to only one- 

 tenth that of the mature eggs. The ovarian wall is thinner than in previous stages, 

 and in the axial portions there are the usual germogenal folds. 



Fig. 137 (plate 38) represents the ovary of a lobster taken August 21. An exami 

 nation of the external eggs shows that they are about six weeks old. The ovary was 

 light green, sparingly flecked with yellow. The individual eggs are greenest at the 

 center, which gives the organ a finely dotted appearance. There is no trace of glands. 



The ovaries of "paper-shells" taken in July, after having produced a brood and 

 molted during the current season, contain ova which measure fully half the diameter 

 of the mature egg. This shows that after ovulation and again after the hatching of 

 the young — that is, during the first, second, and twelfth, thirteenth, and fourteenth 

 mouths after egg-extrusion — the ovarian eggs experience their most rapid growth. 

 (See p. 71, and in particular the description of fig. 138, p. 246.) 



At a still later period, when the ovarian eggs have been growing for the space of 

 nearly two years, ' aud the ova have attained a diameter which is from 80 to 90 per cent 

 that of the ripe egg, the organ has the structure seen in fig. 140, plate 39. There may 

 be considerable variation, but in the specimen from which this drawing was made 

 (female, taken July 30) the ovarian wall is excessively thin and the lumen is packed full 



1 This is an estimate based upon the general facts of growth and development of the ovary, and 

 not upon the observation of single individuals during this lengtli of time. 



