1893.] ii [Hubbard. 



Substituting values ia tlie formula for the sphere V of the nucleus of 

 egg — 14.1372. V of the nucleus of egg s = 8.18125. V of ihe dark 

 body e (or the oblate spheroid) = 5.9070i -f . Therefore o (14.1372) = 

 s (8.1825) + e (5.9070 -J-), leaving an error of onl}' .049, which amounts to 

 very little when considering that each division of the mikrometer only 

 equals. 005 mm. and that the outlines of the dark body not being very de- 

 finite it was difficult to get the precise measurement. 



I think this clearly proves that th<3 body originates from the nucleus. 

 But I do not believe it is by ordinary cell division with the (ormalion of a 

 karyokinetic figure. It seems to be a general extrusion of substance from 

 the nucleus. 



It will be seen from an inspection of Figs. 4-12 that this body is con- 

 siderably smaller in these stages than in smaller eggs (Fig. 3). Whether 

 this is due to reagents causing a shrinkage or whether due to a condensa- 

 tion of substance I am unable to determine. After the egg is 40 // in size 

 (Fig. 5), at which time the body has reached its minimum size, it con- 

 tinues to constantly increase through all of the other sizes. It is nearly 

 always irregular in shape and very seldom has a hard outline which might 

 represent a cell wall. 



Sometimes it assumes very peculiar shapes (see Fig5. 7, 9, 10, 13). 

 The most aberrant form is represented in Fig. 9, where it seems to have a 

 long filament or tail, which is only seen by careful focusing. 



Cymatogaster is viviparous. The eggs of this fish ripen during the 

 months of December, January and February. In an ovary taken on Oc- 

 tober 21 they range in size from .02 mm. to .2 mm. The eggs of Novem- 

 ber 2 begin to show signs of ripening (Fig. 17 («) ). Here the nucleus 

 is a liitle eccentric. The zona radiata is quite distinct and the follicle is 

 well formed. At this stage of maturity there is a peculiar circular region 

 shaded much more darkly than the remainder ot the vitellus. This al- 

 ways appears on the side of the nucleus next to the yolk nucleus and 

 opposite the point of the egg to which the nucleus seems to be moving, 

 The yolk nucleus under consideration is quite close to the periphery of 

 the egg. 



November 30 some of the eggs become about ripe. Fig. 18 represents 

 one which will probably be ripe in January. In this egg the follicle is 

 much developed, the nucleus has become very eccentric and the yolk nu- 

 cleus is nearly touching the periphery of the egg. Up to this time the 

 constant tendency of this body has been to become further and further 

 removed from the nucleus towards tlie periphery of the egg. 



In the stages indicated by Figs. 19 and 20* the body has become slightly 

 changed in appearance. These eggs are nearly ripe. The nucleus has 

 reached its limit of eccentricity, and in one stage (Fig. 20) has lost its cell 

 wall. I have merely indicated its position, which is seen in another sec- 

 tion. The yolk is beginning to collect at the entodermic pole of tlie egg, 

 ». e., around the yolk nucleus. 



* These and succeeding figures are based on preparatious made by Dr. Eigenmann. 



