356 Naohide Yatsii. 



the cytoplasm is consequently much greater than is needed to main- 

 tain the alveolar structure. The cytoplasmic maturation of Delage, 

 ('01), may mean that the cytoplasm becomes overloaded with the 

 hyaloplasm. This is a favorable, if not absolutely necessary, condi- 

 tion for the formation of astral rays as correctly recognized by 

 Mathews ('07, p. 5)7). In this connection one interesting fact may 

 be mentioned, that is, before the dissolution of the germinal vesicle 

 the spermatozoon remains as such in the egg, either the formation of 

 the sperm aster or the swelling of the sperm head being suspended 

 (Fol, '79). Ziegler observed in the egg of a nematode that the sper- 

 matozoon degenerates, when it enters an enucleated fragment from 

 the egg with the germinal vesicle intact ('95, p. 363). Flemming's 

 observation ('91) that the dividing cells of the salamander epithelium 

 stain darker than the resting ones may show that before the recon- 

 struction of the nucleus the cytoplasm is richer in hyaloplasm.'* 



(b) Nuclear Fluid. 



In the living egg the nuclear fluid appears as a homogeneous 

 liquid, not an emulsion of the difFerent fluids as in the cytoplasm. 

 Neither reticular nor alveolar structure is visible. In sections, how- 

 ever, the nuclear substance gives an entirely different aspect from 

 what is seen in the living state. As is shown in Fig 10 (PI. I) the 

 germinal vesicle is traversed by an irregular network. The meshes 

 are not complete ; many free ends of the branches can be observed. 

 The apparent reticular structure of the nuclear fluid is, I think, 

 simply an artifact produced by coagulation. Although there are 

 many cases in which the nucleus actually contains reticulum or 

 alveoles, e. g., in the protozoan nucleus, yet in a good many cases 

 the homogeneity of the nuclear fluid has not been correctly recog- 

 nized (cf. Henneguy, '96, p. 106, Rhumbler, '96). 



It is interesting to note that the nuclear fluid changes its nature 

 the moment the nucleus begins to fade (cf. Lillie, '06, p. 166). Fig. 

 2 and 3 (PI. I) show this relation very clearly. The nuclear fluid 



^Throughout the present paper the figures are from the preparations of 

 Cerehratulus lactciis, luiless otherwise mentioned. 



