No. 2.] THE DEVELOPMENT OF THE NEWT. 311 



The progress and maturation of the spermatozoa after they 

 enter the &gg may be best studied by sections through eggs 

 from two to five hours old. The advance of the spermatozoon 

 into the egg is signalized by the often described streak of 

 pigment (Fig. 23C). This pigment streak, though it is not so 

 prominent in the egg of the newt as in more deeply pigmented 

 eggs, enables the path of the spermatozoon after entrance to be 

 easily traced. It has been thought by some observers (see e.g. 

 Hertwig, '77, p. 49) that the pigment is mechanically carried in 

 from the cortical layer by the onward movement of the sperm- 

 atozoon. While this may be in part true, there is another factor 

 that undoubtedly assists in the production of the pigment 

 streak. The esrsfs of the newt when viewed from the surface 

 show the points of entrance of the spermatozoa each distinctly 

 marked by a spot of pigment. The pigment accumulation at 

 these points forces one to conclude that the male element exerts 

 an attractive influence upon pigment granules comparable to 

 that shown by the poles of the maturation spindle (Fig. 21). 

 This attractive force appears to diminish as the sperm penetrates 

 deeper into the ^%Zy and the pigment granules discarded along 

 the way then form the familiar pigment trail. There is, there- 

 fore, some force connected with both male and female elements 

 that, in certain stages, attracts pigment granules; this force at 

 other stages appears to lapse into quiesence. 



There frequently arises a considerable accumulation of a 

 semi-fluid reticular substance (protoplasm }) around the head of 

 the male element. This accumulation often assumes the form 

 of a mushroom, showing crescentic in sections (Figs. 23B, 23C). 

 The head of the sperm occupies the middle of this area, and 

 the whole effect is such as almost to convey the impression that 

 the yolk granules have been driven out of this region by move- 

 ments of the spermatozoon. I am loth, however, to believe 

 that such is the case, since there is good reason to think that 

 the active movements of the sperm cease after it penetrates 

 the egg. Occasionally a faint filament stretches off behind into 

 the pigment streak and strongly suggests the presence of the 

 tail of the spermatozoon (Fig. 23B, 23C). I am unable, how- 

 ever, to identify it certainly as such. It is not to be seen when 



