4(i4 1'itici rsity of California Publications in Zoology. IT OL - 6 



follicle frequently contains a great variety of stages. Near one 

 margin arc found scattered nuclei in a syncytium; the rest of 

 the follicle is filled with cells with well-defined walls and full of 

 yolk-spheres (pi. 41, fig. 49). The cells are large, about 20ft, 

 with round clear nuclei, druse marginal chromatin and a round 

 central nucleolus. The cytoplasm is reduced to a thin marginal 

 layer in which the nucleus is embedded. The body of the cell is 

 packed with yolk-platelets, from i^./x to 2/i in diameter, granular 

 in composition, and staining rather faintly except with Lyon's 

 blue and toluidin blue, with both of which the platelets stain 

 very intensely. The whole cell breaks out of the follicle and 

 enters the system of yolk-ducts, through which it makes its way 

 to the yolk-reservoir and thence to the uterus. The yolk-plates 

 have been observed by me only within a nucleated cell. The cell 

 as a unit becomes one of the components of the compound egg 

 formed in the uterus. 



This statement is not in agreement with Lonnberg's descrip- 

 tion of conditions in G. urna. He says: "Die Dotterzellen zer- 

 fallen schliesslich, so class nur die Kornchen durch die Gange zu 

 den Eizellen gelangen." That is. only tin- yolk-platelets, not the 

 yolk-cells themselves, enter into the composition of the uterine 

 egg. Aside from the fact that yolk-duets, reservoir, and the 

 beginning of the uterus are all full of typical nucleated yolk- 

 cells, the most cursory examination of the early coils of the uterus 

 shows that the eggs, even before the shell is completely formed, 

 are multicellular. Lonnberg saw this, but interpreted it as evi- 

 dence of a very early cleavage of the ovum. "Die Eifurehung 

 tritt sehr friihzeitig ein, so dass man Eier findet, deren Schalen 

 noch nicht fertig gebildet sind, aber wo das Embryo schon 

 gebildet ist." But a careful examination of such an early uterine 

 egg shows that it contains cells of two kinds, one having the 

 characteristic size, staining reactions and nuclear structure of 

 the ovarian ovum (ov.), and the others typical vitellarian cells 

 (yk. c, pi. 9, tig. 47). Cleavage of the ovum does not begin for 

 some time after the shell is completely formed. Spencer's (1889, 

 p. 145) observations concerning the yolk-gland and his figures 

 of yolk-follicles are very puzzling. His statements are as follows : 



"A difference of structure has been noted above in the case of the 



