174 bulletin: museum of comparative zoology. 



single case sections showed an apparent exception, the spermatozoon 

 having entered an egg while it was still within the medusa, and before 

 the polar cells had been detached. Figure 18 (Plate 2) represents the 

 condition referred to; the smaller vesicle appears to be the sperm 

 nucleus, the larger one has every appearance of a germinative vesicle. 

 As arguments that the latter is such, the following points may be sug- 

 gested: (1) the egg nucleus is usually not so close to the periphery of 

 the egg; (2) the size and shape of the nucleus are characteristic of 

 germinative vesicles just before the first maturation spindle forms 

 (Figs. 5, 7) ; (3) at least one, and possibly two, astral centers are pres- 

 ent (somewhat like Figure 7), a condition not usually found accom- 

 panying egg nuclei ; (4) other eggs in the same medusa had their nuclei 

 in a condition which precedes the formation of the maturation spindles. 



Sections show that while the spermatozoon may enter the egg at any 

 point, it more commonly enters rather close to the egg nucleus (Fig. 

 18). The cones seen at the surface of living eggs may also be recog- 

 nized in those which have been fixed (Figs. 17a, 19b), though this is 

 not always the case (Figs. 18, 19c). Sections of eggs which showed 

 this cone also showed a spermatozoon or sperm nucleus, consequently 

 the cone is to be considered as an entrance cone (Wilson, :00) rather 

 than a true attraction cone. 



Sometimes there is located in the periphery of the egg, and extending 

 from its surface to the sperm nucleus, a differentiated, funnel-shaped 

 region (Figs. 17a, 20a), which one naturally refers to the influence 

 of the spermatozoon. Sometimes the axis of the funnel or cone- 

 shaped region is straight and nearly radial (Fig. 17a), at other times 

 it is more or less curved (Fig. 20a), but its apex coincides with the 

 sperm nucleus, and its broad basal end is always at the periphery of 

 the egg. Similar phenomena, apparently due to similar causes, have 

 been observed in other eggs. They are especially prominent in the 

 eggs of certain amphibians, where the pigment renders the condition 

 more obvious (Schultze, '87, Fick, '93, King, :01), and have also 

 been observed in the earth worm (Foot, '94), in echinoderms (Wilson, 

 '95), etc. An angle has sometimes been found in this "track"; it 

 was interpreted by Roux ('87) as the end of the "entrance path," 

 after which the sperm comes under the influence of the egg nucleus 

 and moves toward this in the "copulation path" ; while Fick considered 

 the angle due to the rotation of the spermatozoon. The "track" 

 in Pennaria never showed this angle, and as a rule was nearly radial 

 and short, leading directly to the egg nucleus, which was usually 

 near the point of entrance of the sperm. In many cases no "track" 



