No. 2.] THE OVARIAN EGG OF LEMULUS. I 31 



fenestrae. The epithelium over the area of the fenestrae, being 

 relieved of this pressure, protrudes through these as evaginated 

 pouches (PI. XIII, Fig. 15). 



The cells lining these follicles are spherical, as compared with 

 the greatly elongated, compressed cells between the follicles. 

 The cell outlines are not so distinct as in the elongated cells, 

 and the epithelial lining of the follicle often appears more like 

 a layer of protoplasm containing nuclei than like a well-marked 

 epithelium of columnar cells. 



In very many cases these follicles are filled with a secretion 

 resembling yolk. This secretion is seen to arise in the cells of 

 the epithelium often in the form of granules, and frequently in 

 the form of a non-stainable mucus-like substance, which is 

 accumulated in large masses, occupying nearly the whole cell. 

 The secretion which is poured into the lumen of the follicle 

 may be discharged through the communication of the follicle 

 with the lumen of the ovarian tube into the latter, the fol- 

 licle in such a case serving the purpose of an ordinary gland. 

 There is no reason for supposing that these lining cells of the 

 follicle differ in any essential respect from those lining the 

 ovarian tube proper, since their difference in form can be 

 accounted for by their freedom from pressure. The epithelium 

 lining the follicles and that lining the tube proper are, in fact, 

 a continuous layer of similar secreting cells, the peculiar 

 arrangement which they have being due solely to the fenes- 

 trated nature of the muscle coat. 



It frequently happens that, instead of being an open space as 

 it is often found to be, or else a space filled with secretion, the 

 lumen of the follicle is filled with large masses of protoplasm 

 in the form of large, ill-defined, irregular cells (PI. XIV, Fig. 

 23). These cells, occupying the entire follicle, are also seen to 

 be secreting, inasmuch as they become filled with yolk-like 

 granules {s.g.), often to such an extent as to entirely obliterate 

 cell boundaries. In such cases the granular secretion appears 

 to arise and accumulate around the nucleus of each cell to such 

 an extent as to obscure the nucleus, and often to render its 

 detection difficult. The chromatin granules of the nuclei are 

 seen between the secretion granules, often apparently imbedded 



