132 Ml/NSOX. [Vol. XV. 



in their substance. The secretion takes a dark coloration in 

 osmic acid, and, like the secretion of the ordinary epithelial 

 cells of the ovarian tube, stains with difficulty, except with such 

 powerful stains as acid fuchsin. Occasionally such a follicle is 

 seen to have been transformed into a mass of non-stainable, 

 homogeneous substance, showing irregular dividing lines, per- 

 haps the original cell boundaries. These lines, probably the 

 last remnants of the protoplasm of the cells originally present 

 in the follicle, stain in haematoxylin. At their intersections 

 are observed deeper staining patches that might suggest the 

 presence of nuclei. 



The large accumulation of secretion here described occurs 

 only in those follicles where an egg is absent. 



Development of the ovary. — In a young animal of one inch 

 or less there are indications of a subcutaneous alveolar tissue 

 between the liver and the carapace. At this stage numerous 

 deeply staining nuclei can be observed lying between the cara- 

 pace and the forming liver. Tlie body of these cells can be 

 seen to be flattened, and the various cells bear a certain fixed 

 relation to one another. The meshes between the cells in- 

 crease, owing perhaps to accumulation of liquids. It then 

 appears that the cells, originally closely packed, now form the 

 thin walls of vesicles or cavities. The nuclei are still prom- 

 inent. Each of these vesicles has a wall of its own, composed 

 •of flattened cells set edge to edge, very much as in the case 

 of lymph spaces in general. As these spaces increase in size 

 the cells of their walls become flatter and the nucleus less 

 distinct. Where two of these spaces are contiguous the wall 

 appears double, as if the two walls had become closely applied. 



In sections of the young animal at this stage, and earlier, 

 there can sometimes be seen between these contiguous walls 

 isolated cells with a distinct, deeply staining nucleus, and a 

 well-defined cell body of protoplasm, having that characteristic 

 clearness which is peculiar to the germ cells during the period 

 of division, previous to the period of growth. The position 

 of these cells corresponds to the position of the ovarian tubes, 

 when they can first be definitely recognized as such. 



In a series of transverse sections the cells are not to be 



