MEMOIliS OF TUE NATIONAL ACADEMY OF SCIENCES. 395 



teristic grauiiliir appearance of the j^eriiiiiial vesicle of tlie i oniig egg. The first trace of tlie yolk 

 (O', O^, O^) appears in tlio outer granular layer which surrouuds the germinal vesicle. Thi.s layer 

 represents primarily the cell protoplasm, in which the yolk is formed. The cell takes on a (Iclinite 

 shape and is very early invested with a follicnlar coat (F. C). In an egg a little older (O") the 

 nucleolus has appeared, and in still older eggs (Fig. G, O, O') a delicate chorion (Ch.) can be 

 seen. This is secreted by the (^ells of the follicnlar envelope (F. C). The growing eggs pass out 

 from the central to the perii)heral parts of the lobe in the sheets of stroma Ix^tween the blood 

 sinuses. Distinct yolk sphendes are very early seen (O') and are of uniform size, but in maturer 

 eggs (Fig. G, O, O') the germinal vesicle is sometimes surrounded by a central layer of small 

 spherules ami a peripheral layer of larger ones. The germiiial vesicle is centrally situated and 

 always contains a single excentric nucleolus, besides stellate masses in the chromatin reti<;nlum.* 

 (v) The Spiny iois^cr (Palinurns). — In the spiny or rock lobster from the Bahamas the ova 

 originate exactly as in Ilomarus, and the structure of the ovary is essentially the same. There 

 are several nucleoli, as in Alpheus. The ovary is not nearly so richly su])plied with blood sinuses 

 as in the cases just considered. This is perhaps correlated with the fact that the amount of yolk 



• Since the above account was written I have been able to stndy the strnctnro of the ovary more thoronghly, 

 and the subjoined notes are largely extr.acted from a preliminary notice on "The Reproductive Organs and Early 

 Stages of Development of the American Lobster." (23.) 



The strnctnre of the mature ovary is somewhat peculiar. The free, unextruded eggs lill the lumen of the 

 ovarian lobes. The lobe or tube itself consists of the proper ovarian tissue and the outer uiusenlar wall, which is 

 very thick. The stroma is characterized by the presi'uce of (jhind-Uke struclun-n, blood sinuses, and immature ova. 

 The glands are in close relation with the growing eggs. They are plaited or folded strinturcs, and consi.st of a single 

 layer of columnar cells, the boundaries of which are indistinct. The lumen of the fold usually contains a granular 

 residue, but often yolk and degenerating nuclei. It seems possible that these structures are comparable to yolk 

 glands, and that their fuuctiou is to supply the growing ova at this stage with a part of their massive food yolk. 

 Three days after the extrusion of the eggs the glandular c:eca have much thicker walls; the rapidly dividing cells 

 are smaller, and their nuclei lie .at various levels. In another ovary of about the same age the glands are relatively 

 very large. The columnar cells are greatly elongated, their nuclei lie at the deeper or outer ends of the cells, .and 

 the lumen of the gland is often completely obscured. The gland forms a kind of egg tube, abutting upon and partly 

 inclosing the growing egg. The columnar cells stop short at the sides of the egg, so that the glandular ciccum resem- 

 bles a narrow bag with an egg pu.shed into its mouth. The glandular cells are directly continuous with those of (he 

 follicle. The axial portion of this ovarian lobe is composed of hollow spaces, blood sinuses, and loose stroiiia, in 

 which very young eggs occur. Degenerating cells occur not only in the stroma, l)ut probably in the developing ova 

 also. In Peripattia Xova; Zcalandkr the yolk is described by Lilian Sheldon as arising not only from the egg proto- 

 plasm, but .also from the follicle cells (T)?). 



When ten to tifteen days have elapsed after egg-laying (eggs in egg-uauplius stage), the gland-like bodies 

 have almost wholly disappeared. The walls of the ca-ca are shrunken and crumpled, and the latter have been 

 crowded to the extreme perijihery of tho ovary. The ovary now contains a solid core of innuature eggs, stroma, and 

 bloodvessels. This is continuous with radial sheets of similar tissue which extend from the center toward the pe- 

 riphery. The outer and more mature masses of ova are thus divided into more or less continuous, longitudinal b.ands. 



At a still later period (eggs with eye pigment, four to five weeks' old ) the glands are j)resent nn-rely as 

 shriveled remn.ants. Later still (lobster taken August 21 ; egg embryos in <a late staged there is no trace of glaml-liko 

 structures. In the ovary of a lobster (taken June 30), with eggs about to hatch, the condition is similar to the last. 

 It is m)w .about eleven months sinre the eggs wore laid, yet the diameter of the largest ovarian ova is only about on< - 

 half that of tlu! mature eggs. The ovarian wall is thinner than in previous stages, .and in the axis of the lobe there 

 are still sheets of very small, immature ova. 



It seems that the bodies which have been described as probable yolk glands are present in the peripheral 

 parts of the ovaries only during tln^ limited pi'riod of from two to throe weeks after the eggs are laid, and when the 

 org ins are recovering from th<^ changes which follow this event. Their strm;ture is quite unlike th.at of bloodvessels 

 or sinuses with which they are intricately associated, and their relation to the growing eggs seems to imply thai 

 they have some functtion to perform in tho nourishment of the peripheral ova. Their short existence, on tho other 

 hand, might lead us to suspect that they were more or less rudimentary structures, or that they wore concerned with 

 the secretion of the gluey substance with which the eggs are coated at tho time they are laid. Their true function, 

 however, remains to bo determined. 



Ovaries which I have examined, taken in summer (.Inly) from lobsters ( "paper shells") which have roci-ntly 

 moulted aud which do not carry eggs, present very thin w.alls, ,an<l the largest ovum measures in diameter about one- 

 half that of tho mature egg. These lobsters have probably hatched a brood the present season .and have afterwards 

 moulted. (Compare tho ovary of the Inbster taken .June 30 above.) 



Some allowance is to bo made for individual ditVerence, but the slow growth of the ov.ariau egg, which wo 

 have traced from the summer when eggs were laid to toe following summer when these eggs were hatched, is very 

 noteworthy, and shows conclusively that the lobster is not an annual breeder. 



