WAGENER, ON GYRODACTYLUS ELEGANS. 209 



riteflns, as previously occurs with the vesicular spot in the 

 germinal spot and itself j and somewhat later with the 

 gErminal spot and germinal vesicle. 



The folloAving process also was directly observed. A 

 globular body^ in every visible property precisely like that just 

 described, occupied the uterus, whilst almost in the middle of 

 the oviduct, which was otherwise empty, projected a small 

 ovum, still retaining its connection with the ovary. Suddenly 

 the first segment globule [ovum] lying in the uterus, threw 

 out an elevation on its upper side, whose base enlarging in 

 the direction of the greatest vertical diameter of the ovum 

 rapidly advanced, forming a progressive constriction, which 

 gradually increased in size and depth. When this groove 

 had reached the middle of the ovum it ceased to extend, and 

 visibly becoming deeper and deeper appeared at last to bisect 

 the ovum. 



Further observation was prevented by the commencing 

 decomposition of the animal, at the end of four hours, during 

 which period the two coherent segment spheres remained 

 perfectly motionless. 



The further process of segmentation, as already remarked 

 by Von Siebold, takes place with great irregularity. 



Perfect cells do not appear to be formed until after this 

 first division of the ovum. Whilst in other cases a nucleus 

 and nucleolus are usually seen to be formed in the ovum or 

 first segment-sphere, and to precede the second division, in 

 the present instance the formation of a nucleus and nucleoli 

 does not commence until after the first constriction has taken 

 place. 



The mode in which nuclei and nucleoli originate, is difficult 

 to follow. It appears as if in the interior of the ovum a 

 [differentiation or] separation of the fluid from the solid 

 elements took place, since a sort of breaking up of the substance 

 may occasionally be remarked in the interior of the substance, 

 manifested by its coarsely granular aspect. Sometimes this 

 appearance might be attributed to the existence of very 

 minute, clear, closely contiguous nuclear vesicles with cor- 

 responding nucleoli, but sometimes this condition was not 

 obvious. 



The nucleus and nucleolus, seen in the two segment-spheres, 

 are of very different sizes. The nucleus is always clear, sharply 

 defined, occasionally round, sometimes oval, or even more or 

 less regularly biscuit- or sausage-shaped. The nucleolus is 

 only more opaque ; in other respects it resembles the nucleus 

 in form. When the nucleolus has attained a certain size it 

 may become elongated and irregularly bent, whilst shallow 



