8 DE. J. F. GEMMILL ON THE DEVELOPMENT OF 



villus-like tufts, on the surface of which they assume an elongated form, many of them 

 being crowded with granules or globules of fatty nature, while others have a large 

 proportion of clear mucoid contents. 



The larger villi rest on a fold of the inner layer of the egg tube-wall, and this fold 

 may contain an extension from the spaces previously described as existing between the 

 inner and outer layers of the gonad-wall. 



The follicle-cells surrounding young and half-grown ova are cubical or polygonal in 

 shape, and provide a covering several layers thick. As growth nears completion, these 

 become reduced to a single layer made up of cubical or flattened cells. Still later 

 they seem to undergo complete degeneration, the eggs when shed being destitute of a 

 cellular covering. 



Practically all the follicle-cells contain fatty granules, mostly small and resembling 

 those within the eggs, but often larger and comparable with ordinary fat-globules. 

 As was indicated above, it is possible that the smaller granules are transferred directly 

 through the vitelline membrane into the ovum during growth. 



There is no definite lumen within the egg-tube, the spaces between the eggs being 

 occupied by follicle-cells, and by a small amount of fluid containing some irregular 

 cells which are probably of leucocytic origin. In some cases masses may be noted 

 which look like the debris of degenerating ova. These masses are without deflnite 

 outline and consist of densely crowded fine yolk-granules, with small nuclei here and 

 there among them. Round the nuclei a certain grouping of the yolk-granules is 

 observable, as if each nucleus was establishing a cell-territory. The nuclei are probably 

 of leucocytic nature. 



Egg-Ducts. — The walls of the egg-ducts contain inner and outer layers corresponding 

 in structure with those of the gonad-tubes, but the gonad sinus-spaces are not 

 continued into the depth of the body-wall. The ducts are lined with ciliated 

 cylindrical epithelium rising into folds and having many cells with clear mucoid 

 contents. The transition between the germinal cells of the egg-tubes and the 

 epithelium of the ducts is quite sudden, and even in immature specimens there 

 is no septum intervening between the contents of the tubes and the lumen of the 

 ducts. 



It is difficult to determine macroscopically the exact number of external genital 

 openings. During active spawning, however, as many as four eggs emerged at the 

 same time, but discretely, from a single interradius. Serial sections of an interradius 

 in the adult showed that each of the gonads had two slit-like terminal ducts formed by 

 the union of several tributary ducts, some of which joined the terminal one within the 

 thickness of the body-wall. In Solaster papposa, according to Mliller and Troschel 

 (quoted from Ludwig, 13, p. 592) and Cu^not (4, p. 623), each gonad has a number of 

 ducts which pierce the body-wall independently, but close together, the small area on 

 which they open being thus sieve-like in character. 



