Ookinesis in Cerebratiilus Lacteus. 363 



hratulus. Indeed it is even wanting in (a) the sperm-, maturation- 

 and segmentation-asters, when just appeared; (&) in any asters 

 immediately after division; (c) in the asters found in the pilidium 

 (Text Fig. A, j and k). In other cases the rays change their 

 nature near the centriole, and give rise to a special zone of archi- 

 ])lasm as is seen in Fig. 58 (PL IV). In other eases a homogeneous 

 area is found between the archiplasm and the centriole. This zone 

 is the centroplasm (= centrosome). A remarkable difference can 

 be noticed after different fixing fluids in its sharpness of outline 

 and its affinity for stain. In still other cases the archiplasm layer 

 is lacking, and the rays radiate directly from the centrosome. In 

 the last cases the centroplasm usually contains the central end of 

 the rays (PI. Ill, Fig. 56). In large cells the centroplasm, at the 

 division of an aster, enlarges and becomes alveolar, as we shall see 

 later (PI. Ill, Figs. 49-53). 



In all probability the centriole has the power of transforming 

 either the cytoplasm, or the archiplasm or rays into centroplasm. 

 The r,ay-system is also beyond doubt produced by the action of the 

 centriole. Some other structures may also be the centre of ray- 

 system as "we shall see later, but in what manner is not kno\vn. 

 Boveri thinks that the centrosome is the producer of the rays ('00, 

 p. 117). Biitschli ('92) and Ehumbler ('96) tried to explain the 

 ray formation as caused by the hygroscopic nature of the centrosome, 

 and, moreover, according to the latter, the disharmony of the growth 

 of the centrosome and the ray-system is due to a peculiar character 

 of certain colloid substance, such that swelling takes place suddenly 

 when a certain amount of water has been absorbed. But the fact 

 that the rays are formed even when there is no centrosome around 

 the centriole and that the centriole^ does not change its physical 

 nature throughout the whole process of ray formation makes it dif- 

 ficult to accept the views of the above cytologists. The ray-forming 

 activity of the centriole, however, seems to cease in the latter part 

 of the growth of the aster, as is shown by the eccentric position of 

 the centriole in old asters. It may, therefore, be safely said that 



*Mauy cytologists call centriole ceiitrosonie. 



