DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 683 
is crenate and the sides are furrowed. In the pike Ransom describes the micropyle as 
trumpet-shaped, and projecting slightly from the surface of the capsule (No. 127, pl. xvi. 
fig. 25, a); while in the minnow, too, the margin is raised around the outer opening of 
the funnel (/bid., p. 456). Stria are occasionally seen in certain pelagic forms, e.g., in 
Trigla gurnardus and Gadus eglefinus, but the margin of the crater is usually sharply 
marked, and the aperture itself very clearly defined without radial markings. When viewed 
in “ full face,” the funnel seems larger than it really is on account of the torsion, so to 
speak, of the zona radiata, which appears as if bent in to form the orifice, a feature ANDRE 
particularly points out (No. 4, p. 199), and to which we have made reference above. 
The micropyle thus varies in appearance. Usually the external opening is the larger ; 
but in some cases this is reversed, a large gaping internal opening being present (vide 
fic. of ovum of G. eglefinus, Pl. I. fig. 14), while the external orifice is small. The 
striations above mentioned are also visible in this case—the whole peri-micropylar region 
being granular, while the granules have a tendency to range themselves in radial lines. 
Near the micropyle in some examples an accessory structure is present, due apparently 
to a granular protrusion of the zona (Pl. I. figs. 11 and 15). In this and other cases 
the micropyle was distant from the germinal area. Fertilisation in pelagic eggs does not 
produce any marked change in the micropyle, certainly none like that described by 
Ransom, and just mentioned. In one instance, beside the micropyle proper, was a 
depression plugged by an ovoid granular structure, while a large group of “ oleaginous” 
spheres lay upon the yolk near the micropyle (PL. I. fig. 17). 
Origin, Position, and Function of the Micropyle-—The mode of origin of the 
Teleostean micropyle is unknown. When first observed in the mature ovum it presents 
the features maintained throughout the subsequent history of the egg. Lrypie describes 
(No. 97, p. 376, fig. 6) the earliest ovarian egg of Trigla hirundo as somewhat pyriform 
and stipitate, recalling, in fact, the stalked ovum of Unio, in which the micropyle marks 
‘the pedicular point of attachment by which the egg adheres to the ovarian capsule, as 
Carus was the first to note. Such an interpretation of the micropyle, as the cicatricule 
left by a pedicle, cannot in the case of the osseous fishes be adopted, and we are still 
left in doubt as to the way in which the aperture arises. 
It is interesting to observe that in many forms the position of the micropyle is 
constant, and corresponds to the germinal pole, where the embryonic area is formed, 
as, indeed, Ransom found in Gastrosteus. In Perca, however, the aperture is turned 
towards the inside of the ege-tube—the ova being fixed in a cylindrical mass, so that the 
possibility of the micropyle being blocked up by adjacent ova is obviated (No. 127, p. 456). 
GeRBE similarly says, “that the micropyle plays an important part, as the dise always 
collects near the place oceupied by it” (No. 57, p. 330). Neither Ransom nor GrrBe 
examined pelagic ova; but from the later observations of Ewart and Brook, it would 
appear that in floating eggs the micropyle is always found in the lower hemisphere 
(No. 55, p. 55). This position is, of course, the reverse of that in stationary demersal ova, 
in which a preformed dise is commonly found in the upper (animal) segment ; whereas in 
