Munson, Organization and Polarity of Protoplasm. 383 



of the hen's egg forms an axis at one end of which the vegetative 

 pole, at the other end the animal pole, is fixed. The position 

 of the two primary germ lapers may therefore be said to be pre~ 

 determined in the ovarian egg, even from the beginning of growth, 

 by the position of the nucleus and centrosome of the oocyte. 



The position of this axis with reference to surrounding cells 

 and tissues is difficult to determine in most eggs. But the ova- 

 rian egg of Limulus is especially favorable in this regard, since 

 its connection with the ovarian tube is a point easily seen. An 

 ovarian tube of Limulus is represented in the diagram fig. 34, 

 pl. Ic. 



Originally the ovary of Limulus consists of strings of ger- 

 minal cells arranged in the form of a network. As the cells mul- 

 tiply the strings form hollow tubes, the cells forming a linirig 

 epithelium of the tube, and being surrounded by a network of 

 muscle fibers. As the original oogonia multiply a differentiation 

 occurs, some of the descendents becoming secreting cells, forming 

 the permanent lining epithelium of the tube. These lining epi- 

 thelial cells correspond to the follicle cells of other eggs; and they 

 seem to have the same nutritive function as ordinary follicle 

 cells have. I have shown that in Clemmys marmorata, the fol- 

 licle cells are originally the sister cells of the egg; and that is pro- 

 bably the case also in Limulus. But, in this case, as the egg 

 grows, it sinks down beneath the epithelium and between the 

 muscle fibers, so that it finally develops outside the tube being 

 connected only at one point with the epithelial cells, through 

 which it doubtless is nourished. In my work on Limulus, I have 

 shown how the ovarian egg is nourished; namely, the secretion 

 of the lining epithelial cells is often supplied so abundantly that 

 it accumulates outside the egg, where it resembles entirely the 

 amorphous food substances of the egg itself. 



The ovarian tube thus formed is organically united with the 

 alveolar tissue of the ovary only along one side fig. 34, x, pl. Ic. 

 At this point, new eggs fig. 34, a, are formed as the tube increases 

 in diameter. Thus we find larger and larger eggs b, c, d, e, f, g, 

 h, i and so on tili we reach a point opposite x, at o, where the 

 first and consequently the largest egg is found. These eggs are, 

 however, discharged into the ovarian tube while still compara- 

 tively small, the true yolk bodies being formed after the egg has 

 left the follicle and entered the tube. 



If the ovarian tube be slit open, and laid out flat, the sur- 

 rounding muscle fibers are seen to be so arranged as to leave 

 oval openings large enough for the eggs to pass through into the 

 tube. The contraction of these muscles may possibly have some- 

 thing to do with the expulsion of the egg into the tube. After 

 this, the egg is apparently nourished by the secretions of the 



