1888.] MICROSCOPICAL JOURNAL. 181 



The purpose of the ovary as an organ is to produce eggs. If we were to state 

 in abstract language the structure of the ovary it would be framed thus : — the 

 ovary is an organ composed of numerous sacks or follicles communicating 

 with a common outlet, the oviduct. The recesses or follicles are shut off 

 from direct communication with the blood spaces of the body by a flat-celled 

 epithelium. Within each follicle there lies one large body, an egg. In most 

 respects this description of the ovary would be equally true of the green 

 gland, or of the liver. 



Unlike them, however, we have the cavity of the follicle not occupied by 

 a secretion, but by a nucleated body possessing many of the peculiarities of a 

 cell. The shape of the follicular epithelium-cells would not interfere with 

 one regarding the ovary as a gland, for variety in shape can be found in the 

 cells of any gland. The egg-, however, is at first sight entirely unlike any- 

 thing found in glands like the green gland or the liver, and we must consider 

 it more carefully. If a very young cray-fish were examined, that ovary would 

 be found to be very unlike its form in the adult. Instead of numerous folli- 

 cles a simple skin would be found of epithelium cells forming a chamber and 

 opening to the outside by a tube. The wall of this chamber, as the cray-fish 

 advances to^vard maturity, becomes covered with small, pimple-like sacks, 

 these sacks being the beginnings of the future follicles. These sacks are at 

 first empty, their walls being composed of cells of what is known as germinal 

 epithelium. 



One cell of the germinal epithelium, apparently exactly like all the others of 

 the follicle, breaks away from the wall of the follicle and takes a position in the 

 cavity of the follicle, and the wall closes up the space where it stood. The 

 cell which has thus been pushed into the cavity of the follicle is at first like 

 the others from among which it came. It is small, with the characteristic 

 nucleus, protoplasm, and outer wall ; but globular, because free from contact 

 on all sides. This cell is the future egg. Why any particular cell is the one 

 to become the future egg rather than another, and whether any cell could 

 have been so distinguished of all the cells of the follicles, no one has thus far 

 been able to positively say, though many have attempted to find an answer. 

 The most careful study of the ovary has not settled this problem ; doubtless, 

 when it is settled, it will help to bring within our I'each the answers to many 

 questions now floating about in a very nebular manner. 



When the egg has thus become diflerentiated from the germinal epithelium 

 or begun a recognizable existence, we can follow it as it at first enlarges in 

 size by the increase in its protoplasm, then later by the addition of deutero- 

 plasm, the follicle also growing larger to accommodate it. We can now see 

 a stronger reason for regarding the egg as a cell. We find grounds from the 

 study of its anatomy merely, but stronger ones from a consideration of its 

 history. The egg can be traced backward from its mature condition to the 

 form of a simple cell of germinal epithelium. When it has been fertilized 

 by the spermatic fluid of the male it goes forward towards the production of 

 a new cray-fish with its multitude of cells with multifarious uses. What a 

 mystery that this single cell should be capable of begetting so complete a 

 creature as ,p cray-fish. 



But the inquiry comes up as we observe this history of the egg and of the 

 follicle, whence comes the protoplasm and the deuteroplasm which go into 

 the young egg in the follicle so that it can become a mature egg? Here we 

 learn the uses of the follicle epithelium. It is partly to protect the egg, but 

 its far more important purpose m to pick food out of the blood and pass it 

 through to the egg. Not only are the follicles of less dignity than the egg, 

 in that they are not to have the distinction of perpetuity as is the egg, but 

 they are fui'ther made to labor for it by ensuring to the egg that only the de- 



