1 96 MUNSON. [Vol. XV. 



the cytoplasm. As these appearances have been described 

 elsewhere, they need not be repeated here. The central re- 

 fringent granule, staining deep red in acid fuchsin and sur- 

 rounded by these radial fibers and metaplasmic zones containing 

 the blue granules, is undoubtedly the centrosome ; and it, with 

 the surrounding structures, constitutes a real sphere. Accord- 

 ing to van Beneden ('87), the sphere consists of a central body 

 (centrosome) surrounded by a clear zone (medullary zone), 

 which again is surrounded by a granular zone (cortical zone). 

 All of these conditions can be seen in the vitelline-body, in the 

 egg of Limulus. According to Boveri ('89, '95), the centrosome 

 is surrounded by a zone of archoplasm, which in some way 

 grows out into the cytoplasm in the form of astral rays, which 

 gradually replace the cytoreticulum. The vitelline-body pre- 

 sents the features of the sphere as defined by Boveri, and also 

 the characteristics of a real aster (Figs. 43-46, 50-52, 54, 55, 

 57. 60). 



But it is the unusual features which this body assumes that 

 offer the greatest difificulties. Some of these are its excentric 

 position, its large size, and the fantastic appearance which it 

 often presents. The more common of these is the great 

 increase in size of the central body (PL XV, Figs. 71, 'j'j \ 

 PI. XVI, Fig. loi), or the apparent absence of a definite central 

 structure ; the concentric arrangement of the fibers ; their 

 great increase or diminution ; the often granular aspect of the 

 body ; the vesicular form which it sometimes assumes ; and 

 finally the combination in various ways of these different fea- 

 tures. An attempt to account for these features will be made 

 in the suggestions that are to be offered in the following 

 chapters on some of the physiological problems of growth and 

 metabolism. 



These features are not foreign to the centrosome and sphere 

 as these are now understood. I will only invite a comparison 

 of some of the forms represented in the plates with the sphere 

 in sperm cells of the salamander as figured by Rawitz ('95) and 

 Meves ('94, '95), and in nerve cells as figured by Lenhossek 

 ('95). Such a comparison will only serve to strengthen the 

 conviction that the vitelline-body is indeed a sphere which not 



