300 Naohide Tatsii. 



time, one an acceleration of the division rate of the centriole and 

 the other an enlargement of the centrosome. One who is familiar 

 with the literature soon finds that number, shape and size are not 

 the criteria of the centriole. Meves describes a group of cen- 

 trioles in the first maturation mitosis of the oligopyrenous sperma- 

 tozoon of Paludina ('03, PI. 3, Figs. 70 and 78). Heidenhain's 

 microcenters in the leucocytes are another example, although 

 these may be brought about by some pathological conditions, 

 as suggested by Boveri ('01, pp. 21 and 22). The spongy or 

 pluricorpuscular centrosomes have been observed by Wilson in 

 the MgCl, egg of Toxopneustes ('01, Figs. 70 and 82). These 

 three examples will suffice tor the present to show that the cen- 

 trioles may vary in number. Generally speaking, the centriole 

 has constant size to a particular kind of cells of an animal, yet 

 considerable periodical fluctuation in size was noticed by the 

 writer in the egg of Cerebratulus. The centriole is as . a rule 

 spherical, yet quite often we meet rod-shaped ones among the 

 "normal" eggs. In abnormally treated eggs the size and shape 

 of the centriole are exceedingly variable as is shown in the MgClz 

 eggs (Toxopneustes) and CaCU eggs (Cerebratulus). (Fig. 10.) 

 From this it will be seen that Vejdovsky and Mrazek's conclusion 

 that "die Centriolen in alien Fallen dieselbe Grosse und Beschaf- 

 fenheit zeigen" seems untenable especially in abnormal cases. 



Now let us consider how the cytasters which have appeared in 

 enucleated fragments differ from the normal aster. The size 

 and number of the dark granules are not constant in the cytaster, 

 while in the normal aster the centrioles are almost of the same 

 size and never exceed two in number. In some cytasters an 

 enormous accumulation of the centroplasm takes place, while 

 in the normal case the growth of the centrosome is limited. As 

 we have already seen, all these abnormalities of the cytasters 

 occur in the whole egg treated with the CaClj solution. We are, 

 therefore, led to the conclusion that the dark granules at the 

 center of the cvtaster of the enucleated Tragments are not mere 

 metaplasmic granules, but real centrioles. 



My experiments and sections of the enucleated fragments are 

 not numerous enough to ascertain the development of the cytaster. 

 I may, however, be able to construct the history out of the material 

 at hand without great error. According to the distribution of the 

 centers in enucleated fragments we shall get two different types 



