MUSEUM OF COMPARATIVE ZOOLOGY. 143 



thirds, which taper only slightly from without inward. The micropylar 

 canal is partially filled with a plug of substance which appears to be con- 

 tinuous with the yolk. The granulosa cells overlying the micropyle do 

 not appear different in size from those which envelop the rest of the egg, 

 but a single cell is sometimes seen to overlie the micropyle in addition 

 to the regular Layer of granulosa cells. In the second stage (Fig. 36, 

 Plate III.) the micropylar canal is narrower than in the first; it no 

 longer tapers gradually from the outside inward, but is slightly nar- 

 rowed at two points, one near the outside and one at its deep end. By 

 the retraction of the yolk from immediate contact with the zona near 

 the micropylar canal in the case of one of the eggs, a space was formed 

 through which could be traced a cord of substance continuous with that 

 which occupied the canal itself. The portion of the substance which trav- 

 ersed this space was funnel-shaped, with the wide end next the yolk. The 

 thickness of the zona does not now differ so greatly in different regions as 

 at the first stage. At some distance from the micropyle in the egg last 

 mentioned (Fig. 36), the inner surface of the zona was raised rather 

 abruptly ; nearer the micropyle it was slightly depressed, but the mar- 

 gin of the canal was raised in the form of a low cone, which thus occu- 

 pied the centre of a very shallow inverted crater, the rim of which was 

 formed by the outer circular elevation. Above the micropyle in the 

 granulosa was a large spheroidal space nearly filled with a granular mass 

 somewhat denser than the yolk. The mass was slightly contracted, leav- 

 ing a narrow space at its periphery. I am in doubt whether to regard it 

 as a cell or not, since no nucleus could be detected. On both sides of this 

 granular mass there were several highly refractive homogeneous bodies 

 (Fig. 36, x x). It is however doubtful if they have any significance in 

 relation to the micropyle. The granulosa cells at this stage are tall 

 and have elongated nuclei, which are broad at the exterior end, and 

 taper towards the egg membranes. 



Notemigonus chrymleucus. 



The ovary of this species contained ova in four stages of development 

 on May 9th. In all but the smallest eggs the zona radiata was present. 

 The largest had a diameter of 0.6 mm., and the zona varied gradually 

 from a thickness of 2 /x on one side of the egg to that of 4 /z on the 

 opposite side. The pore-canals are very fine, being almost invisible in 

 balsam preparations. 



The micropyle was observed in only a single case ; it was found in 

 the middle of the thickest portion of the membrane, which is exactly in 



